lean dome Feb 21, 2021, 7:26 PM

#

If you've got an iterable over tuples, and you want to pass each tuple to a function that accepts a tuple, just don't unpack the tuples at all.

rancid patio Feb 21, 2021, 7:26 PM

#

this 👍

dense cloud Feb 21, 2021, 10:17 PM

#

Hello guys! I have a question regarding DFS/BFS.
I understand that DFS is backtracking/ exploring, and BFS is finding a pathway. But how do i determine when to use either one?

vast halo Feb 21, 2021, 11:18 PM

#

is anyone available to help with a for loop problem please ping me

fiery cosmos Feb 21, 2021, 11:55 PM

#

does anybody

#

know

#

how to implement karatsuba algorithm in python

#

switching

#

from cpp to python

onyx root Feb 22, 2021, 12:09 AM

#

fiery cosmos how to implement karatsuba algorithm in python

interesting. why implement it?

fiery cosmos Feb 22, 2021, 12:11 AM

#

idk

#

learning

#

for cpp

#

*cp

onyx root Feb 22, 2021, 12:13 AM

#

CPython uses karatsuba for very large numbers

kindred coyote Feb 22, 2021, 12:25 AM

#

is there anyway to make this code faster: ```py
import sys
raw_input = sys.stdin.readline
m = int(raw_input())
n = int(raw_input())
brushes = raw_input()
stroke = []

colors = [['B' for _ in range(n)] for _ in range(m)]
for i in range(int(brushes)):
g = raw_input().split(' ')
if stroke.count(g) == 1:
stroke.remove(g)
else:
stroke.append(g)
def changeColumn(num,colors,index):
if num == 0:
return colors
colors[num-1][index] = 'G' if colors[num-1][index] == 'B' else 'B'
num -= 1
changeColumn(num,colors,index)

def countGold(c,options,i):
if options == []:
s = 0
for l in c:
s += l.count("G")
print(s)
return
area = options[i][0]
times = int(options[i][1]) - 1
if area == "R":
c[times] = list(''.join(c[times]).replace("G","A").replace("B","G").replace("A","B"))
elif area == "C":
changeColumn(m,c,times)

options.remove(options[i])
countGold(c,options,i)

countGold(colors,stroke,0)

onyx root Feb 22, 2021, 12:39 AM

#

kindred coyote is there anyway to make this code faster: ```py import sys raw_input = sys.stdin...

is it too slow?

#

@kindred coyote changeColumn is recursive, which is unusual. you can use a loop.

#

also, it returns a value, but nothing seems to use it?

kindred coyote Feb 22, 2021, 1:00 AM

#

onyx root is it too slow?

Actually I found the problem. It's generating colors. A program will need to generate a 10^6 x 10^6 array in less than 2-3 seconds

#

I need to solve this problem without generating an array

#

as that takes up too much time

dapper sapphire Feb 22, 2021, 1:51 AM

#

is there a good resource to learn syntax of python linked list? I understand the concept theoretically that the current node points to memory address of the next node and so on. But I find it a bit confusing to implement it. And every other website I go to has a different way of implementing it.

brisk saddle Feb 22, 2021, 1:59 AM

#

@dapper sapphire it is pretty simple.

in essence, you have a head node, and a tail node.

#

let us say you have these 5 values that you wish to initiate with the Linked List:
1, 2, 3, 4, 5

#

and you have a head field, and a tail field in your class.

#

the tail represents the last node in the Linked List, while the head represents the first.

#

do you follow so far?

dreamy arrow Feb 22, 2021, 2:09 AM

#

he wanted an answer for exams and its wright because for each time in n you will move length -1 which means you will move length *n

dapper sapphire Feb 22, 2021, 3:27 AM

#

brisk saddle let us say you have these 5 values that you wish to initiate with the Linked Lis...

Yeah, I follow it so far, the tail would point to None and head would point to the first element.

brisk saddle Feb 22, 2021, 3:28 AM

#

nope, the tail actually points to the first element once it is initialized.

#

so normally when i implement my linked lists, i pop(0) the first element off the list of initialized values, and assign that to the head, and the tail to that as well.

#

once you do that, you begin to "chain" values.

#

def __init__(self, *entries):
    entries = list(entries)
    self.head = Node(entries.pop(0))
    self.tail = self.head

#

so when you "chain" values, you loop through the remaining values to initialize, and for each element, you do the following:

create a new node. we will call it n for now.
set the next_node field of the current tail to n
set the tail to n

#

this is so the cycle can repeat for the next node you add.

#

@dapper sapphire let me know if you want me to rephrase anything, or you do not understand it.

dapper sapphire Feb 22, 2021, 3:34 AM

#

wait can we do *enteries? I thought we cant use a pointer in Python. and would having a pointer or not having a pointer make a difference in this case?

brisk saddle Feb 22, 2021, 3:34 AM

#

*entries defines a varadic argument called entries

#

the * does not mean "pointer to type entries" like it does in C.

#

it just means "this is a varadic argument."

#

this is so you could do this, and have it be valid syntax:

my_list = LinkedList(1, 2, 3, 4, 5)

instead of

my_list = LinkedList([1, 2, 3, 4, 5])

#

you following with that?

dapper sapphire Feb 22, 2021, 3:41 AM

#

oh right ok I get it so with variadic argument we dont have to worry about specifying the number of parameters.
on line 3 you pop the 0th element and assign the value to head. On line 4 you assign the popped value also to the tail.

brisk saddle Feb 22, 2021, 3:41 AM

#

yup!

#

let me know if you need help with any other datastructures, or you want to clear some things up.

#

i would be glad to help.

dapper sapphire Feb 22, 2021, 3:42 AM

#

wait is that it?? That's all for linked list?

brisk saddle Feb 22, 2021, 3:42 AM

#

yeah pretty much.

#

that is all it takes to initialize one.

#

there are other operations, and you also need to setup iteration, i can help you with that if you would like.

#

but yeah, that is basically all it takes to create one. Linked Lists are extremely easy to initialize.

dapper sapphire Feb 22, 2021, 3:45 AM

#

So what you just did with 4 lines of code to initialize a linked list, is this similar to the below code where we create a Node class and a LinkedList class:

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class LinkedList:
    def __init__(self):
        self.head = None

brisk saddle Feb 22, 2021, 3:46 AM

#

yeah that is pretty similar to how i would write it.

#

i mean i could show you how to setup a Linked List in C as well if you wanted me to, but this is a Python server.. the option is always there, though!

#

assuming you do not know.

dapper sapphire Feb 22, 2021, 3:55 AM

#

I think C would just confuse me even though I have programmed in it before. Python would be fine. But hey when you do:

self.head = Node(entries.pop(0))
self.tail = self.head

You are not pointing anything to None? both head and tail point to the 0th element.

brisk saddle Feb 22, 2021, 3:56 AM

#

yeah, that is intentional.

#

it is because if we start looping through with the tail as None, we would have no way to add something to the end of the list without using the head field.

#

we do not want to reassign the head field during initialization.

dapper sapphire Feb 22, 2021, 3:57 AM

#

ok so how would you create an add method?

#

to insert elements to the list.

brisk saddle Feb 22, 2021, 3:57 AM

#

what form of adding? insertion, or appending?

dapper sapphire Feb 22, 2021, 3:58 AM

#

appending

brisk saddle Feb 22, 2021, 3:58 AM

#

oh, appending is easy. you do the exact same thing you did during initialization with the tail field.

#

except it is in it's own function.

dapper sapphire Feb 22, 2021, 4:01 AM

#

are you creating function based linked list?

brisk saddle Feb 22, 2021, 4:01 AM

#

well of course. classes have methods bound to them.

dapper sapphire Feb 22, 2021, 4:01 AM

#

I mean I guess, we could create a linked list either way.

brisk saddle Feb 22, 2021, 4:05 AM

#

or by "function-based" did you mean in a way similar to how C operates on datastructures?

dapper sapphire Feb 22, 2021, 4:05 AM

#

so suppose the code you wrote was in a class called Node, then would we create a add method like below:

def add(self, data):
  self.head = Node(data)

brisk saddle Feb 22, 2021, 4:05 AM

#

using functions in a file that accepts a struct or something along those lines as an argument?

#

that seems more like a prepend method, but yeah, close.

#

you are missing an important factor, though.

#

that will essentially unlink the entire Linked List, since you are not assigning the next field of the new node to the previous head.

#

so make sure you do that.

dapper sapphire Feb 22, 2021, 4:16 AM

#

def add(self, data):
  temp = Node(data)
  temp.next = self.head
  self.head = temp

So something like this.

brisk saddle Feb 22, 2021, 4:16 AM

#

bingo

#

whenever you add or remove any Nodes into your Linked List, make sure you check you are not preventing access to other parts of the list.

#

just a general word of advice, really.

dapper sapphire Feb 22, 2021, 4:21 AM

#

How did you get comfortable with linked lists? Just practice?

brisk saddle Feb 22, 2021, 4:22 AM

#

more or less, yeah

#

i am familiar with a few more datastructures.

#

Hashtables, Queues, Stacks, most types of Trees, Sets, and Arrays.

#

those are the ones i am aware of how to create.

#

Queues and Stacks are essentially just Linked Lists or Arrays with operations that only operate on the bottom or top.

dapper sapphire Feb 22, 2021, 4:24 AM

#

Yeah I was doing Queues and Stacks yesterday and I found those pretty easy to understand and implement.

brisk saddle Feb 22, 2021, 4:25 AM

#

they are, yeah.

#

Hashtables and Trees are my favorite to implement.

dapper sapphire Feb 22, 2021, 4:26 AM

#

When you say you implemented a hashtable, you mean, you created a dictionary?

brisk saddle Feb 22, 2021, 4:27 AM

#

yeah, Hashtables are an implementation of a Dictionary, also known as Associative Arrays.

dapper sapphire Feb 22, 2021, 4:30 AM

#

Hashtables are next on my list of things to implement. Because I use dictionaries a lot on different projects and I find it really powerful. Hey man, really appreciate all the help!!

brisk saddle Feb 22, 2021, 4:30 AM

#

anytime. feel free to ask me for help on implementing them Hashtables. i would be glad to help out.

dapper sapphire Feb 22, 2021, 4:32 AM

#

I am glad that I scrolled down to the server and posted the question here. Yeah of course, much appreciated!

brisk saddle Feb 22, 2021, 4:33 AM

#

anyway, i think i am going to head off to bed now.

#

sleep tight.

icy crane Feb 22, 2021, 4:40 AM

#

Hm

#

.topic does it work here

grand havenBOT Feb 22, 2021, 4:40 AM

#

**No topics found for this channel.**

Suggest more topics here!

icy crane Feb 22, 2021, 4:40 AM

#

Lolll

dreamy arrow Feb 22, 2021, 6:53 AM

#

get it at the base case condition of the recursive function

knotty void Feb 22, 2021, 7:33 AM

#

are array lists better than single linked list when you want to store a very big data base?

kindred coyote Feb 22, 2021, 7:33 AM

#

import sys
raw_input = sys.stdin.readline
m = int(raw_input())
n = int(raw_input())
brushes = int(raw_input())

listed_rows = []
listed_columns = []
gold = 0
duplicates = []
for i in range(brushes):
    g = raw_input().split()
    g[1] = int(g[1])
    if g in duplicates:
        continue
    else:
        duplicates.append(g)
        if g[0] == "R":
            gold += (n - len(listed_columns))
            gold -= len(listed_columns)
            listed_rows.append(g[1])
        if g[0] == "C":
            gold += (m - len(listed_rows))
            gold -= len(listed_rows)
            listed_columns.append(g[1]-1)
print(gold)
``` does any1 know how to make this even faster? I still get a time limit exceeded error

#

(Time Limit is 4 seconds)

knotty void Feb 22, 2021, 7:35 AM

#

kindred coyote ```py import sys raw_input = sys.stdin.readline m = int(raw_input()) n = int(raw...

what are you trying to do tho?

kindred coyote Feb 22, 2021, 7:35 AM

#

lemme send problem

#

A new and upcoming artist has a unique way to create checkered patterns. The idea is to
use an M-by-N canvas which is initially entirely black. Then the artist repeatedly chooses
a row or column and runs their magic brush along the row or column. The brush changes
the colour of each cell in the row or column from black to gold or gold to black.
Given the artist’s choices, your job is to determine how much gold appears in the pattern
determined by these choices.

#

The first line of input will be a positive integer M. The second line of input will be a positive
integer N. The third line of input will be a positive integer K. The remaining input will be
K lines giving the choices made by the artist. Each of these lines will either be R followed
by a single space and then an integer which is a row number, or C followed by a single space
and then an integer which is a column number. Rows are numbered top down from 1 to M.
Columns are numbered left to right from 1 to N.

#

and u output how many gold squares there r

#

I also have this code: ```py
for i in range(int(brushes)):
g = raw_input().split(' ')
if stroke.count(g) == 1:
stroke.remove(g)
else:
stroke.append(g)

def changeColumn(num,colors,index):
if num == 0:
return colors
colors[num-1][index] = 'G' if colors[num-1][index] == 'B' else 'B'
num -= 1
changeColumn(num,colors,index)

def countGold(c,options,i):
if options == []:
f = 0
for l in c:
f += l.count("G")
print(f)
return
area = options[i][0]
times = int(options[i][1]) - 1
if area == "R":
c[times] = list(''.join(c[times]).replace("G","A").replace("B","G").replace("A","B"))
else:
changeColumn(m,c,times)

options.remove(options[i])
countGold(c,options,i)

countGold(colors,stroke,0)

knotty void Feb 22, 2021, 7:39 AM

#

are you sure you need to iterate through the entire list?

kindred coyote Feb 22, 2021, 7:40 AM

#

It's basically saying this: ```
Enter a number M
The next M lines, enter....

#

so in the 1st code, the for loop is a must unless there's another way to do that

winter schooner Feb 22, 2021, 7:47 AM

#

can anyone help me converting this bash to python

#

#!/bin/bash

packageInfo.bash

Purpose: Generates a report to displaying specified information of installed software

USAGE: ./packageInfo.bash [application-name]

Author: * INSERT YOUR NAME *

Date: * CURRENT DATE *

if [ $(whoami) != "root" ] # only runs if root
then
echo "You must be logged in as root." >&2
exit 1
fi

if [ $# -ne 1 ]
then
echo "Your command must have a application-name as argument" >&2
echo "USAGE: $0 [application-name]" >&2
exit 1
fi

Create report title (echo with -e option allows newline \n character to be used)

echo -e "\nSOFTWARE PACKAGE INFORMATION REPORT" > /root/package-info.txt
echo -e "Date: $(date +'%A %B %d, %Y (%H:%M:%p)')\n\n " >> /root/package-info.txt

Clear screen and use Here Document to display select on report items to read into variable

clear
cat <<+
Available Package Information Items:

Name
Summary
Version
License
Source
URL
+
read -p "Enter word(s) shown above separated by spaces: " choice

Convert spaces to pipe symbol (|)

processedChoice=$(echo $choice | sed 's/ /|/g')

Use sed with extended regular expressions to only print those matching report elements

rpm -qi $1 | sed -r -n "/^($processedChoice)/ p" >> /root/package-info.txt

cat <<+
File "/root/package-info.txt" has been created
+

Save, set permissions, and then run that shell script for the application gedit. Did it create that report? Try running the script without an argument - What did it do?
Use the wget command to download, study, and run the following shell scripts on-line:

worn narwhal Feb 22, 2021, 7:50 AM

#

What is an algorithm? My understanding of writing algorithms is figuring out what exactly to do with code to find the results you want. Is this an accurate definition?

topaz pulsar Feb 22, 2021, 9:00 AM

#

@kindred coyote can you send a link to this problem, I want to test a solution I think i have using ||sets||

dry crow Feb 22, 2021, 9:56 AM

#

same

kindred coyote Feb 22, 2021, 10:11 AM

#

topaz pulsar <@!629120968425472010> can you send a link to this problem, I want to test a sol...

ur right. solution is this: ```py
import sys
rw = sys.stdin.readline
M = int(rw())
N = int(rw())
choices = set()
K = int(rw())
for i in range(K):
g = input()
if g in choices:
choices.remove(g)
else:
choices.add(g)

numR = 0
numC = 0
s = 0
for choice in choices:
if choice[0] == "R":
numR += 1
elif choice[0] == "C":
numC += 1

for choice in choices:
if choice[0] == "R":
# numR += 1
s += N - numC
elif choice[0] == "C":
# numC += 1
s += M - numR
print(s)

#

moral of the story: searching lists r more expensive than searching sets when it comes to bigger numbers

topaz pulsar Feb 22, 2021, 10:22 AM

#

what I was planning on was have a set of row numbers and column numbers, then for each input, add or remove that number from the appropriate set depending on if it exists or not (because if the same row is chosen twice it cancels out) then at the end, the number of gold tiles will be M * len(columns) + N * len(rows) - 2 * len(columns) * len(rows) i think, because thats the number of tiles that are gold because of the rows + the numbre of tiles made gold because of the columns, minus the overlap

#

so that would be O(K) time and O(N + M) space

#

i think thats similar to what you did but the only real difference being that final for-loop to calculate s you may be able yo make O(1) using M * numC + N * numR - 2 * numC * numR

vocal gorge Feb 22, 2021, 10:47 AM

#

dreamy arrow he wanted an answer for exams and its wright because for each time in n you will...

Really don't get what you mean. Did you intend to reply to that message specifically (me responding to someone asking for help with an essay)?

#

@dreamy arrow And if you meant my earlier analysis of that code snippet's complexity - no, it's n!, as the plot proves.

rustic sparrow Feb 22, 2021, 2:06 PM

#

we have this question for school but none of us can find the logic error, we've been staring at it for half an hour.

vocal gorge Feb 22, 2021, 2:09 PM

#

the only problem I see is with the loop

#

but it's less a logic error, and more like an undeclared name

#

because, well, response is not set anywhere

rustic sparrow Feb 22, 2021, 2:11 PM

#

I think they mean it as some sort of snippet from a larger program

#

so it is probably declared somewhere else

vocal gorge Feb 22, 2021, 2:14 PM

#

That's true, but it's also not changed over the course of the loop

#

So that loop will either not execute at all, if response is not "Y", or it will loop forever if it is.

#

There's no code that allows exiting the loop via X as it states.

rustic sparrow Feb 22, 2021, 2:47 PM

#

ok, thanks for the help!

#

I found the answer, every time you enter x to exit the loop it adds 1 to rCount anyway so rCount ends up wrong.

vocal gorge Feb 22, 2021, 3:01 PM

#

lol, so you're not supposed to notice that there's also no input being taken?

agile sundial Feb 22, 2021, 3:02 PM

#

input is being taken though right?

rustic sparrow Feb 22, 2021, 3:02 PM

#

type is equal to the input

#

i think

brazen glade Feb 22, 2021, 3:03 PM

#

Is this a snippet from an existing language or pseudocode?

rustic sparrow Feb 22, 2021, 3:03 PM

#

pseudocode

brazen glade Feb 22, 2021, 3:03 PM

#

Okay thanks

agile sundial Feb 22, 2021, 3:14 PM

#

reverse a doubly linked list 😔

brisk saddle Feb 22, 2021, 3:54 PM

#

i refuse to believe i just heard someone say "array list"

#

@mystic basin i mean yeah i guess.

agile sundial Feb 22, 2021, 3:55 PM

#

brisk saddle i refuse to believe i just heard someone say "array list"

what's wrong with that lol

brisk saddle Feb 22, 2021, 3:55 PM

#

nothing that just sounds odd

#

i did not know an "array list" was a thing.

agile sundial Feb 22, 2021, 3:55 PM

#

it's a class in java lol

brisk saddle Feb 22, 2021, 3:55 PM

#

🤨

#

it is?

#

what is it?

agile sundial Feb 22, 2021, 3:55 PM

#

yeah, although it shouldn't really be used

#

it's like a vector

brisk saddle Feb 22, 2021, 3:55 PM

#

why

#

i see

agile sundial Feb 22, 2021, 3:56 PM

#

like python lists

brisk saddle Feb 22, 2021, 3:56 PM

#

yeah

#

i thought it was another case of Java just being special, like with Hashtables and Hashmaps being subtly different things (not sure if that is still true)

agile sundial Feb 22, 2021, 3:56 PM

#

yeah, they're different, but hashtable isn't really used anymore

brisk saddle Feb 22, 2021, 3:57 PM

#

fair enough.

#

anyway reversing a Linked List sounds wild.

agile sundial Feb 22, 2021, 3:57 PM

#

doesn't sound too difficult

#

yeah, it's not that difficult

brisk saddle Feb 22, 2021, 3:58 PM

#

it does not, but as far as i know modifying something as you loop through it is not a good idea.

but maybe it does not involve that, not sure. never tried it.

#

you could potentially just construct a new Linked List, though?

#

that is my first thought.

agile sundial Feb 22, 2021, 4:09 PM

#

yeah, but i think the challenge is doing it in place

brisk saddle Feb 22, 2021, 4:55 PM

#

mostly yeah

old rover Feb 22, 2021, 6:00 PM

#

so does anyone have any good resources to start learning these

#

or books

#

i'm not doing a bootcamp to learn how to do interview questions so anything would be helpful

brisk saddle Feb 22, 2021, 6:01 PM

#

i do not have any books, but i started with a Linked List, so maybe do some Googling and find out how to implement one.

#

i could quickly explain right now, though.

#

Linked Lists are a pretty important datastructure to understand in order to implement some other datastructures.

#

at least, the idea of "linking" Nodes is.

old rover Feb 22, 2021, 6:02 PM

#

all i know is the meme about reversing a linked list

brisk saddle Feb 22, 2021, 6:02 PM

#

so i highly suggest you start there.

old rover Feb 22, 2021, 6:02 PM

#

ok i will check it out

#

yeah uh i read a couple chapters and my head started spinning

brisk saddle Feb 22, 2021, 6:03 PM

#

i remember a Crash Course Computer Science video introduced me into Linked Lists and it did a pretty good job of explaining them.

old rover Feb 22, 2021, 6:03 PM

#

ok

#

and you would recommend doing a lot of problems right

brisk saddle Feb 22, 2021, 6:03 PM

#

yeah, probably.

old rover Feb 22, 2021, 6:04 PM

#

i want to create at least one or two portfolio things before i go ham over hackerrank and leetcode

brisk saddle Feb 22, 2021, 6:04 PM

#

especially if you want to go into interviews for it.

old rover Feb 22, 2021, 6:04 PM

#

ok great thanks

#

can i bring the hackerrank and leetcode questions here too or should i only ask in help channels

brisk saddle Feb 22, 2021, 6:05 PM

#

i mean i do not see anything wrong with asking here.

#

just do not ask questions about Euler challenges i believe.

old rover Feb 22, 2021, 6:05 PM

#

ok great

brisk saddle Feb 22, 2021, 6:05 PM

#

you can get in trouble for posting answers to those i think.

#

not sure if the staff here enforce that, or not.

old rover Feb 22, 2021, 6:05 PM

#

pls i can't even do list comprehension bc i've never seen it before

brisk saddle Feb 22, 2021, 6:06 PM

#

that might be after the one hundredth question, though.

old rover Feb 22, 2021, 6:06 PM

#

that doesn't have much to do w DSA

brisk saddle Feb 22, 2021, 6:06 PM

#

List Comprehension is just when you construct a new list based off another iterator.

old rover Feb 22, 2021, 6:06 PM

#

i can google list comprehension questions and try and solve those

brisk saddle Feb 22, 2021, 6:06 PM

#

x = [n for n in range(10)]

puts all the numbers from zero to nine in the list.

old rover Feb 22, 2021, 6:07 PM

#

i don't get what n for n is tho

brisk saddle Feb 22, 2021, 6:07 PM

#

it is equivalent to this:

x = []

for n in range(10):
    x.append(n)

old rover Feb 22, 2021, 6:07 PM

#

n for n is just syntax

brisk saddle Feb 22, 2021, 6:08 PM

#

yeah, it might be better to represent comprehension like this:

#

n = [(expression) (iterator)]

#

x = [n + 5 for n in range(10)]

#

this will put every number zero to nine, add five to it, then put it into the list.

#

the for loop bit is essentially just where you get your variable from, and the expression describes how that variable should be mutated before being put into the list.

#

in this case, we add five to it.

#

but this is off-topic to the channel, so i guess i will stop here.

old rover Feb 22, 2021, 6:10 PM

#

sorry i asked

#

i'll come back once i work my way up to DS/algo

brisk saddle Feb 22, 2021, 6:10 PM

#

it is no problem

old rover Feb 22, 2021, 6:10 PM

#

thank you

brisk saddle Feb 22, 2021, 6:10 PM

#

anytime

drowsy minnow Feb 22, 2021, 6:32 PM

#

Is anyone free to just look over an algo solution I created? I got it to run and I think pretty effiecntly but I'm at the point where I want to be able to see how to improve my method of code.

uneven jungle Feb 22, 2021, 7:33 PM

#

go

#

@drowsy minnow

drowsy minnow Feb 22, 2021, 7:38 PM

#

def load(wordList):
    trie = {}
    for word in wordList:
        addWordToTrie(trie, word, 0)
    return trie

def addWordToTrie(d, word, idx):
    if idx >= len(word):
        d['leaf']=True
        return
    if word[idx] not in d:
        d[word[idx]] = {'leaf':False}
    addWordToTrie(d[word[idx]], word, idx+1)

def findWords(trie, word, currentWord):
    myWords = set()      
    for letter in word:
        if letter in trie:
            newWord = currentWord + letter
            if trie[letter]['leaf']:
                myWords.add(newWord)
            myWords = myWords.union(findWords(trie[letter], word, newWord))
    return myWords

def main(keypads, wordlist):
    results = []
    minLength = 5
    trie = load(wordlist)
    
    for pad in keypads:
        count = 0
        for word in sorted(findWords(trie, pad, "")):
            if len(word) >= minLength:
                count = count+1
                
        results.append(count)
    return results


wordlist= ['APPLE', 'PLEAS', 'PLEASE']
keypads = ['AELWXYZ','AELPXYZ','AELPSXY','SAELPRT','XAEBSKY']
print(main(keypads, wordlist))

#

You're attempting to solve a puzzle in an escape room with your team.
You need to open a door to get to the next stage.
There are several doors, each with a different keypad on it.
The keypads each have 7 keys, containing 7 distinct letters.
The instructions state that one of the keypads will open the correct door leading to the next stage.
Your job is to find a word that unlocks the correct keypad.
After struggling for some time, the escape room leader gives a clue.
The first letter of the keypad is guaranteed to be in the word that opens the door.
We will call this letter the "key" letter.
The goal of this exercise is to come up with as many words possible that your team can test out on the keypads and find the correct combination to go the next stage of the game.

#

WHAT YOU KNOW:

The correct combination will be a valid english word.
The words are at least 5 letters long, with no maximum length.
The "key" letter will be in the correct answer.
The words do not contain any letters outside the seven letters on the keypad.
Letters may be reused, inlcuding the "key" letter.

For our purposes, we'll express each set of keypad letters as a string of length 7, where the first letter (the one at posistion 0), is the key letter.
An array of integers. Each Integer should be the number of valid words in the correspdoning lock.

REQUIREMENTS:

Implement a function numKeypadSolutions(wordlist, keypads) that follows the function signature below:

INPUT:

wordlist: An array of strings. This is your list of "valid English words" for the purposes of the following puzzles.
keypads: An array of strings. Each string is the sequence of letters on the keypad.

OUTPUT:

An array of integers. Each integer should be the number of valid words in the corresponding lock.

#

CONSTRAINTS:

Both the wordlist and the keypad letters will be supplied in all capital letters.
All words in the wordlist will be of length 5 or greater.
Every sequnece of keypad letters will be of exactly length 7.
Every sequence of keypad letters will consist of 7 distinct letters.

EXAMPLE:
INPUT:
wordlist: ['APPLE', 'PLEAS', 'PLEASE']
keypads: ['AELWXYZ', 'AELPXYZ', 'AELPSXY', 'SAELPRT', 'XAEBKSY']
expected output: [0,1,3,2,0]

EXPLANATION:

None of the words in the wordlist can be formed from the letters in keypad 0.
Only APPLE is valid for keypad 1.
APPLE, PLEAS, and PLEASE are valid for keypad 2.
Only PLEAS, and PLEASE are valid for keypad 3, since APPLE does not contain the key letter "S".
None of the words are valid for keypad 4, since none contain the key letter "X".

#

I realize my solution doesn't apply the "key" letter though so that's what I'm attempting to throw in right now but it keeps messing everything up. *

#

The expected output should be [0,1,3,2,0] and I get [0,1,3,3,0] since I haven't been able to throw in the if check properly for the index of keypad I think

uneven jungle Feb 22, 2021, 7:58 PM

#

One thing, is that you can break the test if the tested letter fails, this cuts down the time complexity

fiery cosmos Feb 22, 2021, 8:30 PM

#

hi

brisk saddle Feb 22, 2021, 8:37 PM

#

good afternoon

uneven jungle Feb 22, 2021, 8:37 PM

#

result = [0]*len(keypads)
for word in wordlist:
for keypad in keypads:
for letter in word:
add = False
if letter not in keypad:
break
else:
add = True
if add == True:
result[keypads.index(keypad)] +=1
print(result) @drowsy minnow

#

@drowsy minnow there's an error in the expected output

#

I believe it should be 3 just as you yielded

#

I posted an alternative without new dicts and stuff

drowsy minnow Feb 22, 2021, 8:44 PM

#

Thanks I will check this out!

#

This is just within the main function correct? I

#

ah yeah okay I see...

uneven jungle Feb 22, 2021, 8:46 PM

#

you can cut the word length a bit by making a set, but I doubt that operation is faster than just running one extra round

#

if you have mega long words it's better to make them in to sets

vocal gorge Feb 22, 2021, 8:53 PM

#

agile sundial it's like a vector

https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html
If I'm reading this right, it is a vector - it's different from Vector by lack of synchronisation, so bad things can happen if you try accessing it from several threads.

#

though I didn't know Vector was synchronized, so it's more like ArrayList is the normal vector-like thingie in Java

spiral scaffold Feb 22, 2021, 9:33 PM

#

can binary trees contain duplicate elements?

#

can't tell if they're supposed to be unique or not

brisk saddle Feb 22, 2021, 10:02 PM

#

@spiral scaffold of course they can

#

if by elements you mean Nodes containing the same value

spiral scaffold Feb 22, 2021, 10:22 PM

#

huh

#

ok thnx 🙂

brisk saddle Feb 22, 2021, 10:53 PM

#

no problem.

quaint summit Feb 22, 2021, 11:49 PM

#

Hello there, I'm trying to make a program that defines the ID in a string and process it. I already made it with a full string (I made a censor algorithm which defines the word that I defined and changes those words into "censored"). But I can't make it with an integer in a string. I can't convert the string into integer in a for loop. Can you help me please?

#

brave oak Feb 22, 2021, 11:51 PM

#

quaint summit Hello there, I'm trying to make a program that defines the ID in a string and pr...

what exactly do you want to do

#

find big numbers and remove them?

quaint summit Feb 22, 2021, 11:51 PM

#

Yes. Exactly.

#

I just want to define the numbers in string.

brave oak Feb 22, 2021, 11:52 PM

#

use regex?

quaint summit Feb 22, 2021, 11:53 PM

#

I'm a newbie programmer and I don't know exactly what that is.

brave oak Feb 22, 2021, 11:53 PM

#

!e

import re

print(re.sub(r'\d{10,}', '<replaced>', 'abc def 123 456 1234567890123 ghi jklmnopqr'))

halcyon plankBOT Feb 22, 2021, 11:53 PM

#

@brave oak :white_check_mark: Your eval job has completed with return code 0.

abc def 123 456 <replaced> ghi jklmnopqr

quaint summit Feb 22, 2021, 11:53 PM

#

I'll give it a look

brave oak Feb 22, 2021, 11:53 PM

#

something like that, yeah

quaint summit Feb 22, 2021, 11:54 PM

#

Alright, thanks a lot ^^

visual cipher Feb 22, 2021, 11:54 PM

#

So I hvae an assignment from my teacher to add up quarters, nickels, pennies, etc and get the dollar and cent amount, and then get the dollar and cent amount separately from each other

#

would I just use the split function and split on the decimal? He doesn't say at all how to do it

#

or is there like another way to do it

brave oak Feb 22, 2021, 11:55 PM

#

visual cipher would I just use the split function and split on the decimal? He doesn't say at ...

you'd be adding numbers, right

visual cipher Feb 22, 2021, 11:55 PM

#

yes

brave oak Feb 22, 2021, 11:55 PM

#

why would you have a string to split

visual cipher Feb 22, 2021, 11:55 PM

#

because it would end up to be like $2.38

#

I need to get the dollar and cent separated

brave oak Feb 22, 2021, 11:55 PM

#

visual cipher because it would end up to be like $2.38

no

visual cipher Feb 22, 2021, 11:55 PM

#

unless im just tweaking and not understanding this

brave oak Feb 22, 2021, 11:55 PM

#

think about it

#

this way

#

the various coins

#

are multiples

#

of a cent

#

you add them all up

#

you get a final number.

#

that represents the number of cents

#

in the result

#

THEN you can convert it into other forms

#

one of which is the dollar and cent amount with a dollar sign

brave oak Feb 22, 2021, 11:56 PM

#

brave oak one of which is the dollar and cent amount with a dollar sign

(string)

#

or just get the number of dollars in that amount

#

(int)

visual cipher Feb 22, 2021, 11:57 PM

#

addOutput = (quarters * 0.25) + (dimes * 0.10) + (nickels * 0.05) + (pennies * 0.01)

#

This is what I have

#

so far

#

It gives me 2.05 with a certain input

brave oak Feb 22, 2021, 11:57 PM

#

aaaAAaaaaaa

#

snake_case please

#

anyway

brave oak Feb 22, 2021, 11:58 PM

#

visual cipher ```addOutput = (quarters * 0.25) + (dimes * 0.10) + (nickels * 0.05) + (pennies ...

this would give you

#

the number of dollars

#

with cents as the fractional part

#

I would suggest

#

you store the number of cents

#

as an int instead

random tendon Feb 23, 2021, 12:04 AM

#

how to create a data structure and a alogrithm

agile sundial Feb 23, 2021, 12:05 AM

#

download the latest firmware for your organic neural net

rich veldt Feb 23, 2021, 12:28 AM

#

Hi everyone soleone know what's the condition in a* Algorithm when f(n) is duplicated!!?

keen hearth Feb 23, 2021, 1:19 AM

#

rich veldt Hi everyone soleone know what's the condition in a* Algorithm when f(n) is dupl...

Hey 🙂 I'm not sure I understand what you mean. Could you elaborate?

placid lantern Feb 23, 2021, 1:47 AM

#

Is there an easy way to get the total numbers of unique items over multiple lists? Say I have a list {h, y, e, w} and a list {a, c, h, e} the total number of unique elements would be 6 while the total elements would be 8. The problem is I'm doing this with about 4k items over a couple hundred different lists so I need an efficient way of doing it.

agile sundial Feb 23, 2021, 1:49 AM

#

4k items total?

#

or 4k each

placid lantern Feb 23, 2021, 1:51 AM

#

4k items total

agile sundial Feb 23, 2021, 1:51 AM

#

just throwing them into a set should be fast enough

placid lantern Feb 23, 2021, 1:58 AM

#

I dont know why I didnt think of that

#

Im so dumb

#

thanks

warm orbit Feb 23, 2021, 2:43 AM

#

algorithms?

#

I'm struggling with coming up for a cross product between two n-dimensional vectors.
I only have 2-d and 3-d

def cross_product(a,b):
    if a==b or isinstance(a,int)or isinstance(b,int):return(0,0,0)
    if not(hasattr(a,'__iter__')and hasattr(b,'__iter__'))or len(a)!=len(b)or not len(a):return NotImplemented
    if len(a)==2:return(0,0,((a[0]**2+a[1]**2)**0.5)*((b[0]**2+b[1]**2)**0.5))
    elif len(a)==3:
        """| i  j  k |
           | a0 a1 a2|
           | b0 b1 b2|"""
        return(
            a[1]*b[2]-a[2]*b[1],
            b[0]*a[2]-a[0]*b[2],
            a[0]*b[1]-a[1]*b[0]
        )
    else:return NotImplemented

#

is there even such thing as a 4-dimensional cross product?

hard bane Feb 23, 2021, 3:30 AM

#

warm orbit is there even such thing as a 4-dimensional cross product?

You can can any arbitrary number of dimensions. That is what makes linear algebra so unintuitive.

warm orbit Feb 23, 2021, 3:33 AM

#

which direction would the cross product point in in 4 dimensions, then?

#

what is a cross product in higher dimensions?

teal haven Feb 23, 2021, 5:21 AM

#

no idea tbh

latent wasp Feb 23, 2021, 11:51 AM

#

Hey guysI have a list of dicts that is generated with this:

    today = datetime.combine(date.today(), time())
    data_list = []
    time = today

    while True:
        if time.timestamp() < datetime.now().timestamp():
            data_list.append({int(time.timestamp()): {time:time.strftime('%I%p'), 'success': 0, 'fail': 0}})
            time += timedelta(hours=3)
        else:
            break

While I iterate through data_list is there a way I can get the key of each item in the list?
This is how the data list looks

[{1614031200: {'time': '12AM', 'success': 0, 'fail': 0}}, {1614042000: {'time': '03AM', 'success': 0, 'fail': 0}}, {1614052800: {'time': '06AM', 'success': 0, 'fail': 0}}, {1614063600: {'time': '09AM', 'success': 0, 'fail': 0}}, {1614074400: {'time': '12PM', 'success': 0, 'fail': 0}}]

#

Oh never mind I found it:

keys = all_keys = set().union(*(d.keys() for d in data_list))

coral loom Feb 23, 2021, 12:37 PM

#

👋 Are there any ways I could append values from a current predefined Pandas dataframe to a new column in a new created dataframe?

lone creek Feb 23, 2021, 4:42 PM

#

warm orbit which direction would the cross product point in in 4 dimensions, then?

when in 3D you do a cross product of 3 (or more i think) vecs you obtain a 4D vector, then in 4D if you do a cross product of some vecs you obtain a 5D vec, and so on

#

it always goes up by one dimension (given that you have enough vectors occuping all the dimensions i suppose)

raw quest Feb 23, 2021, 4:55 PM

#

So I just got this curve which is the result of a genetic algorithm simulation depending on the selection rate for the TSP : https://media.discordapp.net/attachments/780135902524997642/813810960140992512/SR_0.9_to_1.png

I find really weird what happen near 100% selection rate, is that supposed to happen?
Or do you think it's related to my program?
this was a zoom I made with 10 different selection value btw 0.9 and 1, here is the global curve (with 10 points again) https://cdn.discordapp.com/attachments/780135902524997642/813809866895523911/selection_rate_graph.png

#

I can't see any reason why 100% selection rate get way better results than 98%

vocal gorge Feb 23, 2021, 5:15 PM

#

warm orbit I'm struggling with coming up for a cross product between two *n*-dimensional ve...

@hard bane I believe cross product is only defined for 3d, actually - it's a pretty weird operation in that regard.
In exterior algebra terms, [a,b] is defined as *(a ^ b), where ^ is the exterior product and * the Hodge star operator. Now, * maps k-forms to n-k-forms, and for vectors (a vector is a 1-form) a,b, a ^ b is a 2-form. As a result, *(a ^ b) is a n-2-form, which is a vector (1-form) only for n=3.

#

So you can define the cross product for an artibrary number of dimensions, but in general it takes two vectors and returns an n-2-form. Only in 3d is the result a vector itself.

#

It's also mentioned on Wiki, apparently:
https://en.wikipedia.org/wiki/Cross_product#Exterior_product

As mentioned above, the cross product can be interpreted as the exterior product in three dimensions by using the Hodge star operator to map 2-vectors to vectors. The Hodge dual of the exterior product yields an (n − 2)-vector, which is a natural generalization of the cross product in any number of dimensions.

wary wadi Feb 23, 2021, 10:15 PM

#

i require a very basic a-star implementation that could be used for older python versions, so i dug through google and found one... but it is broken... (funny thing is, it is actually copied over the years by people trying to educate people on pathfinding)

my math is just not good enough to fix this simple version of a*.. i was wondering if there is a enthusiast out there that can help me out?

https://pastebin.com/VrG34ypR

feel free to tag me if you're interested... thanks!

warm orbit Feb 23, 2021, 10:31 PM

#

What's an a star?

agile sundial Feb 23, 2021, 10:31 PM

#

it's a an gaseous ball

#

there's also an algorithm called A*

boreal depot Feb 23, 2021, 10:35 PM

#

I'm currently I'm using a bubble sort in my project, but it takes FOREVER to sort 10k+ lines in the currently edited file.
Here is my code: https://github.com/ayourk/HostsManager/blob/main/hostsman.py
During the bubble sort, I also check for duplicates and mess with them appropriately. Is there something I could use that is better/faster/more efficient? I don't have direct access to the editor_lines buffer, but I can move around the buffer using positions. This is a tkinter app and it mostly works.

agile sundial Feb 23, 2021, 10:36 PM

#

is the function in question mnuToolSort

boreal depot Feb 23, 2021, 10:36 PM

#

It's around line 650

agile sundial Feb 23, 2021, 10:36 PM

#

gotcha

#

must you use your own implementation?

boreal depot Feb 23, 2021, 10:37 PM

#

Is there a better way that can also check for dupes?

agile sundial Feb 23, 2021, 10:38 PM

#

where are you checking for duplicates?

boreal depot Feb 23, 2021, 10:39 PM

#

Line 679

agile sundial Feb 23, 2021, 10:40 PM

#

since there's a lot of clutter in your code, and i don't really know what's going on, could you just describe how you're doing that

boreal depot Feb 23, 2021, 10:41 PM

#

Nested double for loop setup for bubble sort, the Try..except section fetches 2 consecutive lines from the buffer and splits them out into lists. Each list should contain at least 2 elements to be valid for sorting. The 2nd item in the list is compared for sorting and checked to see if it is a duplicate.

austere sparrow Feb 23, 2021, 10:42 PM

#

https://github.com/ayourk/HostsManager/blob/main/hostsman.py#L649
Here you're doing quite a lot of stuff while sorting, so it's not very easy to see the logic.
I would suggest doing this:

Make a function that takes a list of hosts (as dicts/tuples/your own classes) and turns them into tkinter stuff
Then use the built-in sorted/list.sort to sort the list

boreal depot Feb 23, 2021, 10:43 PM

#

The user has an option to exclude some lines from sorting. A series of lines can be sorted while leaving the rest of the edit buffer intact.

austere sparrow Feb 23, 2021, 10:44 PM

#

Sure, but you can do all the transformations with the data on the lists, not hot-swapping the graphical objects.

#

It will be much easier to just work with a list.

boreal depot Feb 23, 2021, 10:46 PM

#

When loading the file, not all items are qualified to fit into a list. And the hosts file that I'm using is about 70k entries in addition to all the other comment lines, etc.

#

I'm concerned about memory usage a little.

austere sparrow Feb 23, 2021, 10:46 PM

#

Here you'll basically have to implement an efficient algorithm like mergesort or quicksort on scratch. Which is not very hard, but if you're going to be modifying the graphics on every swap, it's going to be very slow.

boreal depot Feb 23, 2021, 10:47 PM

#

Merge sort would be my goal for this app as new files could be inserted into the buffer and I'd love to sort them/check for dupes as they are being loaded

austere sparrow Feb 23, 2021, 10:47 PM

#

Sorting or removing duplicates from a 70k-sized list is going to be very fast.

#

Certainly faster than mutating a bunch of tkinter stuff along the way

boreal depot Feb 23, 2021, 10:48 PM

#

I just realize that my app is a text editor first, and went that route.

austere sparrow Feb 23, 2021, 10:49 PM

#

If every entry is 100 bytes, then the entire file will take up about 7 MB, which is less than half the memory needed for an interpreter on its own

#

If you use bytes, that is.

#

If you use str, it's going to be more like 30 MB

boreal depot Feb 23, 2021, 10:50 PM

#

The lists/dicts still need to be transferred back and forth from the edit buffer though, right?

austere sparrow Feb 23, 2021, 10:50 PM

#

wdym?

boreal depot Feb 23, 2021, 10:51 PM

#

Or are you saying for the sort alone, just load everything into a list and then do somelist.sort() and put things back into the edit buffer later?

austere sparrow Feb 23, 2021, 10:52 PM

#

What is the program supposed to be doing?

boreal depot Feb 23, 2021, 10:53 PM

#

Open /etc/hosts files that can include comment lines, hosts definitions and in some cases blank lines. In mine, I have a header that is 65 lines long.

austere sparrow Feb 23, 2021, 10:54 PM

#

So it should take N hosts files, merge them, sort them and remove duplicate lines?

boreal depot Feb 23, 2021, 10:55 PM

#

Correct, and at the same time, allowing some lines to exist as comments/extra white space outside of the specified sort range.

austere sparrow Feb 23, 2021, 10:55 PM

#

Why can't that be done with standard unix tools like sed and uniq?

#

and why do you need a GUI?

boreal depot Feb 23, 2021, 10:57 PM

#

Some hosts lines have comments at the end of them (list length is > 2) and some of them don't. These are treated as unique entries when in fact they aren't. Also, I'm trying to consolidate those comments onto the duplicate host (see line 687).

#

the GUI is there to allow the user to make changes manually.

austere sparrow Feb 23, 2021, 10:59 PM

#

I see

#

well, the easiest and fastest way to do it would be to split the program into two parts:

a function that applies all the transformations (sorting, filtering out lines etc.) to a list of lines
all the GUI stuff

boreal depot Feb 23, 2021, 11:02 PM

#

My problem is if I go that route, how do I know which lines/list entries I need to update when the user makes a change? I already know how to detect the modified flag of the edit buffer.

austere sparrow Feb 23, 2021, 11:04 PM

#

But the user only makes the changes after you've sorted and filtered the lines, right?

boreal depot Feb 23, 2021, 11:05 PM

#

The user loads the file into the edit buffer
The user optionally chooses to sort/filter the buffer

austere sparrow Feb 23, 2021, 11:07 PM

#

Okay. So when the user presses the "sort" button, you can read the text from the editor widget, sort it, and then write the new contents back in.

boreal depot Feb 23, 2021, 11:08 PM

#

Yeah. That's what I'm doing now. I just know my way is not very efficient. I went with bubble sort since that was the sort I could remember back from my CompSci 101 days.

austere sparrow Feb 23, 2021, 11:09 PM

#

No, you're sorting them in-place in the widget. What I'm suggesting is getting the text as a string, turn it into a list of lines, and sort the list (which is fast).

boreal depot Feb 23, 2021, 11:10 PM

#

For sorting the list/dict, can I sort based on 1 field contained in that line using a space as a field separator?

#

Each line I use the str.split to at most 3 list entries and only compare dupes on the 2nd entry.

austere sparrow Feb 23, 2021, 11:11 PM

#

boreal depot For sorting the list/dict, can I sort based on 1 field contained in that line us...

Yes. You can pass in an optional key function.

#

.sort() is like sorted, but in-place

boreal depot Feb 23, 2021, 11:13 PM

#

so in this case xs is the list to sort? Can lists contain lists? I haven't looked that close at python's data structures yet.

#

If so, then I could break each line down in advance into a list and store each line in its list form.

austere sparrow Feb 23, 2021, 11:17 PM

#

Are you coming from a C background?

boreal depot Feb 23, 2021, 11:17 PM

#

Mostly.

austere sparrow Feb 23, 2021, 11:18 PM

#

Yes, Python lists can contain anything. Basically, a list is just a dynamic array of pointers.

#

!e

users = [
  {"name": "Bob", "age": 42}, 
  {"handle": "@alice", "age": 50},
  {"handle": "@charlie", "age": 19},
]

def key(user):
    return user["age"]

print(sorted(users, key=key))

halcyon plankBOT Feb 23, 2021, 11:20 PM

#

@austere sparrow :white_check_mark: Your eval job has completed with return code 0.

[{'handle': '@charlie', 'age': 19}, {'name': 'Bob', 'age': 42}, {'handle': '@alice', 'age': 50}]

austere sparrow Feb 23, 2021, 11:22 PM

#

!e
You might also want to check out dataclass, which is like a C struct

from dataclasses import dataclass

@dataclass
class User:
    name: str
    age: int

alice = User(name="alice", age=35)
print(alice)
print(alice.name, alice.age)

halcyon plankBOT Feb 23, 2021, 11:22 PM

#

@austere sparrow :white_check_mark: Your eval job has completed with return code 0.

001 | User(name='alice', age=35)
002 | alice 35

austere sparrow Feb 23, 2021, 11:23 PM

#

(the type annotations don't do anything at runtime, they're just there for documentation)

boreal depot Feb 23, 2021, 11:24 PM

#

So I could do key=lambda: linekey(x) and make sure in the linekey func to always compare against the 2nd list entry?

austere sparrow Feb 23, 2021, 11:24 PM

#

yep. or just key=linekey

#

just like you would do in C's quicksort

boreal depot Feb 23, 2021, 11:25 PM

#

!e

halcyon plankBOT Feb 23, 2021, 11:25 PM

#

You are not allowed to use that command here. Please use the #bot-commands channel instead.

austere sparrow Feb 23, 2021, 11:25 PM

#

(it takes a comparison function instead of a key function, but otherwise same idea)

boreal depot Feb 23, 2021, 11:26 PM

#

sample data:

0.0.0.0 00fun.com
0.0.0.0 00fun.com #[Tracking.Cookie]
0.0.0.0 zzhc.vnet.cn
0.0.0.0 nabijaj-internetowo.eu```

#

So the plan would be to break down each line into a list causing a list such that:

hostentries = [
  ["0.0.0.0", "00fun.com"],
  ["0.0.0.0", "00fun.com", "#[Tracking.Cookie]"],
  ["0.0.0.0", "zzhc.vnet.cn"],
  ["0.0.0.0", "nabijaj-internetowo.eu"]
]```

austere sparrow Feb 23, 2021, 11:32 PM

#

Yes, that would work. Then you could have a function like

def key(entry):
    if len(entry) < 2:
        return "".join(entry)
    return entry[1]
# or:
def key(entry):
    if len(entry) < 2:
        return "".join(entry)
    host, domain, *_ = entry
    return domain

#

I suppose you won't have any blank lines?

boreal depot Feb 23, 2021, 11:33 PM

#

Correct, blank lines are considered bad for the sorted range. Also considered bad are where list items are < 2 per line.

#

I've also built in a check to make sure that list_item[0]'s are all equal.

#

And after I'm done, I put the spaces back in for the
" ".join()

#

Forcing invalid lines to the top/beginning of the list would be acceptable.

austere sparrow Feb 23, 2021, 11:37 PM

#

or maybe just remove them

boreal depot Feb 23, 2021, 11:38 PM

#

Removing them could make it difficult to do a 1:1 replacement within the edit buffer?

austere sparrow Feb 23, 2021, 11:38 PM

#

what do you mean?

boreal depot Feb 23, 2021, 11:38 PM

#

After doing the sort, the edit buffer would need to be rewritten.

#

Then the user can manually edit after the sort completes.

austere sparrow Feb 23, 2021, 11:39 PM

#

you mean, the user won't have the chance to rearrange the lines if you remove them?

boreal depot Feb 23, 2021, 11:41 PM

#

reducing the number of lines will be problematic for the dialog I built. I did build in a failsafe to recheck the number of lines and update the EOL range so it isn't impossible. I think it might be best to at least bring the bad lines to the top of the range so that the user can manually delete those lines if he/she wishes.

#

Unless they are dupes of course. But dupe handling could be handled in 1 pass after the sort completes too.

austere sparrow Feb 23, 2021, 11:42 PM

#

Standalone comments and blank lines don't make much sense if you sort the lines, right? Because now there isn't necessarily a block to which the comment applies

boreal depot Feb 23, 2021, 11:44 PM

#

That is why I have that beautify filter that I'll be incorporating in the selected line range before the sort. Most of that will already be done. Now if there is an easy way to combine 5 regexp's into 1, I'd really love that.

austere sparrow Feb 23, 2021, 11:45 PM

#

what do you mean by combining regexes?

boreal depot Feb 23, 2021, 11:47 PM

#

Lines 583, 595, 607, 618, & 633 are where I filter out bad stuff from a user selected range with spinboxes.

#

I have to use TCL regexp's here because of tkinter

austere sparrow Feb 23, 2021, 11:48 PM

#

You could use |, right?

boreal depot Feb 23, 2021, 11:48 PM

#

I delete text matching those regex's

austere sparrow Feb 23, 2021, 11:48 PM

#

austere sparrow You could use `|`, right?

foo|bar|baz = either foo, bar, or baz

#

AFAIK, when reading from a file Python converts all line endings to \n, but that's more of an aside

boreal depot Feb 23, 2021, 11:50 PM

#

Some of these didn't work in my testing:
http://tcl.tk/man/tcl8.5/TclCmd/re_syntax.htm

austere sparrow Feb 23, 2021, 11:52 PM

#

Well, I don't know much about Tcl/Tk, so can't really help here. Maybe ask in #user-interfaces.

boreal depot Feb 23, 2021, 11:52 PM

#

I've tried there. Last time I asked there I got crickets

#

I'll try that | operator and do some tests.

austere sparrow Feb 23, 2021, 11:54 PM

#

if that doesn't work, you can just use Python's re module

boreal depot Feb 23, 2021, 11:54 PM

#

That means going back and forth with the edit buffer 😾

#

I'll deal with that with the sort since it is an overall improvement.

austere sparrow Feb 23, 2021, 11:55 PM

#

If you want an overview of Python's data structures:
https://docs.python.org/3/library/stdtypes.html
https://docs.python.org/3/library/datatypes.html
you might also be interested in this section:
https://docs.python.org/3/library/filesys.html

boreal depot Feb 23, 2021, 11:55 PM

#

I've been reviewing some of those docs. I learn best by examples though.

austere sparrow Feb 23, 2021, 11:56 PM

#

many of those have examples, like https://docs.python.org/3/library/collections.html#defaultdict-examples

#

anyway, I'll go to sleep now

boreal depot Feb 23, 2021, 11:57 PM

#

thanks, sleep well

austere sparrow Feb 23, 2021, 11:57 PM

#

@boreal depot next time you should probably open a help channel, check out #❓｜how-to-get-help

boreal depot Feb 23, 2021, 11:57 PM

#

I haven't much success with them either.

#

These topic specific channels have been fruitful though (most of the time).

austere sparrow Feb 23, 2021, 11:59 PM

#

Also, https://docs.python.org/3/tutorial/index.html is a pretty dense introduction to Python, and you can pick the sections you want. Not very suited for total beginners IMO, but good if you are already familiar with programming.

boreal depot Feb 23, 2021, 11:59 PM

#

I think I've progressed a bit beyond that.

hearty badge Feb 24, 2021, 1:43 AM

#

I'm trying to do this problem https://open.kattis.com/problems/almostperfect
This is my solution but it's too slow. What could i do to make it faster? I'm kinda new to python and only read about generators and yield keyword. Would that make it significant faster or do i need to rethink my approach to the problem?

import sys
x = sys.stdin.readlines()


for line in x:
    n = line.strip('\n').split(' ')
    n = int(n[0])
    result = 0
    for i in range(1, n):
        if n % i == 0:
            result = result + i
    if result == n:
        print(f"{n} perfect")
    elif (n - result) * 1 <= 2:
        print(f"{n} almost perfect")
    else:
        print(f"{n} not perfect")

glossy breach Feb 24, 2021, 2:14 AM

#

You only have to check integers from 1 to sqrt(n)

#

If you find 1 divisor of n, let's say i in the range[1, sqrt(n)] then there's a corresponding divisor to i in range[sqrt(n), n] which is n / i

#

So the complexity would be O(sqrt(n)) instead of O(n) like you're doing

brisk saddle Feb 24, 2021, 2:23 AM

#

https://cdn.discordapp.com/attachments/291284109232308226/813958856932851743/unknown.png

#

alright so i am implementing MergeSort, and i am going to see if i am understanding this correctly.

is it incorrect in describing this as:
while both lists are not empty, pop off the first elements of both, and compare them. append them to their correct list.

then, do the same thing again for both lists, since they might have leftover elements if they are not of the same length.

hearty badge Feb 24, 2021, 2:47 AM

#

@glossy breach Alright thank you so much! Will try it out!

glossy breach Feb 24, 2021, 2:49 AM

#

brisk saddle alright so i am implementing MergeSort, and i am going to see if i am understand...

Yeah, that's correct

brisk saddle Feb 24, 2021, 3:02 AM

#

alright, thank you.

pearl trout Feb 24, 2021, 3:28 AM

#

is it just me who is taught that python is slowest while solving problems or its just the py algo which sucks that creates a TLE, be my guest and please make me understand it properly

agile sundial Feb 24, 2021, 3:37 AM

#

for competitive programming, python is very very slow, compared to other choices liike cpp

#

for example, you might have to write an O(n log n) algo in python, while an O(n^2) might work in cpp

brisk saddle Feb 24, 2021, 5:06 AM

#

thoughts?

agile sundial Feb 24, 2021, 5:06 AM

#

sure

balmy siren Feb 24, 2021, 6:19 AM

#

If nodes in the tree (which aren't at height 'h') are filled with both the children then, does it mean the tree is called complete binary tree ?

dapper sapphire Feb 24, 2021, 6:25 AM

#

pearl trout is it just me who is taught that python is slowest while solving problems or its...

By slow you mean in terms of computation speed? Which would make sense because you dont have to worry about mallocing and freeing memory, which would make the process of writing code in C/C++ slow.

brisk saddle Feb 24, 2021, 6:42 AM

#

i have implemented QuickSort, as well.

#

def quicksort(source: list) -> list:
    if len(source) <= 1:
        return source

    # Divide
    source_copy = source.copy()
    pivot_index = round(len(source) / 2)
    pivot = source_copy.pop(pivot_index)

    # Re-arrange
    greater, lesser = [], []

    for cmp_val in source_copy:
        if cmp_val >= pivot:
            greater.append(cmp_val)
        else:
            lesser.append(cmp_val)

    # Conquer
    greater = quicksort(greater)
    lesser = quicksort(lesser)

    # Merge
    return greater + [pivot] + lesser

#

it works perfectly fine, but does anyone see any issues with my implementation?

#

i did not get this completely wrong, did i?

brisk saddle Feb 24, 2021, 6:59 AM

#

@brave oak hey, would you mind giving me a hand here?

#

if you are free, at all.

#

@balmy siren a "complete" binary tree means that each node has either zero, or two children.

#

oh wait, i might be confusing "full" with complete here.

#

A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible.

#

this is what a "Complete" binary tree looks like.

#

🤨

balmy siren Feb 24, 2021, 7:07 AM

#

Yeah that's actually a strict binary tree, where each node has either two children or none

brisk saddle Feb 24, 2021, 7:08 AM

#

i mean.. does a non-strict binary tree allow for one child as well, then?

balmy siren Feb 24, 2021, 7:08 AM

#

Yes as long as it's not a "full or perfect"

brisk saddle Feb 24, 2021, 7:08 AM

#

complete, full, perfect, jeez.

balmy siren Feb 24, 2021, 7:08 AM

#

In "full or perfect" binary tree, each node should have two children and all the leafs are at same level

brisk saddle Feb 24, 2021, 7:09 AM

#

ah alright, got it. i probably cannot answer your question then. sorry. =(

balmy siren Feb 24, 2021, 7:09 AM

#

brisk saddle complete, full, perfect, jeez.

I am little confused in a complete binary tree, as you can see all the leafs aren't at same level, G at 2 and all another leafs are at 3 (counting from 0)

#

No worries 👍

brisk saddle Feb 24, 2021, 7:10 AM

#

yeah i was a bit confused at that as well.

#

https://web.cecs.pdx.edu/~sheard/course/Cs163/Doc/FullvsComplete.html

hmm, maybe this website is not very accurate.

balmy siren Feb 24, 2021, 7:11 AM

#

But afaik, those nodes which aren't at height h (in the picture you mentioned A, B, C, D, E) should have either None or both the children..

brisk saddle Feb 24, 2021, 7:22 AM

#

#algos-and-data-structs message

#

it works perfectly fine, but does anyone see any issues with my implementation?
i did not get this completely wrong, did i?

#

i think i followed the description on Wikipedia pretty well, but another set of eyes is always nice in a situation like this.

lean dome Feb 24, 2021, 7:25 AM

#

brisk saddle i have implemented QuickSort, as well.

Seems correct. It would be much faster if you avoided the copying and instead updated the original list in place, but this algorithm looks right.

brisk saddle Feb 24, 2021, 7:25 AM

#

thinkin alright, sick.
thank you!

main bison Feb 24, 2021, 7:26 AM

#

it does not account for repeated values in the pivot, is that needed?

brisk saddle Feb 24, 2021, 7:26 AM

#

repeated values in the pivot? i think i saw something on the Wikipedia page relating to that.

#

one moment.

lean dome Feb 24, 2021, 7:26 AM

#

Ah, the return at the end should have lesser on the left and greater on the right

#

Otherwise you're returning the list in reverse order

brisk saddle Feb 24, 2021, 7:27 AM

#

alright. i will fix both of the things you brought up.

#

With a partitioning algorithm such as the Lomuto partition scheme described above (even one that chooses good pivot values), quicksort exhibits poor performance for inputs that contain many repeated elements. The problem is clearly apparent when all the input elements are equal: at each recursion, the left partition is empty (no input values are less than the pivot), and the right partition has only decreased by one element (the pivot is removed).

#

thinkin

#

@main bison is this what you were referring to?

main bison Feb 24, 2021, 7:27 AM

#

no, im refering to your code

#

pivot = source_copy.pop(pivot_index)

#

this is one value

brisk saddle Feb 24, 2021, 7:28 AM

#

my thought process was so i could do this:

return lesser + [pivot] + greater

i originally had it saved as the index of the pivot, rather than the value itself.
it just saved a line or two of code.

#

does that answer?

lean dome Feb 24, 2021, 7:29 AM

#

main bison this is one value

That seems fine to me. It removes the item with that index from the list, leaving any other items with the same value alone. Those will get put into greater when it loops over the list

brisk saddle Feb 24, 2021, 7:30 AM

#

^

#

it is so the loop for separating lesser and greater elements does not include the pivot itself.

#

sorry, i should have mentioned that.

#

i am not sure if that is 100% needed, though.

#

it was just something i added as a precaution.

main bison Feb 24, 2021, 7:31 AM

#

what if there are 100 values of the pivot at once?

brisk saddle Feb 24, 2021, 7:31 AM

#

thinkin

#

i can test that, one moment.

#

seems to work fine, was the 100 pivots bit hyperbole, or did you actually mean one hundred pivots?

lean dome Feb 24, 2021, 7:33 AM

#

If there's a problem with duplicate pivots, I'm not seeing it.

brisk saddle Feb 24, 2021, 7:33 AM

#

well, the only way to make sure is to test it a bunch of times.
i will just to make sure.

thanks, you two! if you notice anything else i have done wrong, let me know.

#

also i tested it with one hundred two's just to be sure.

#

seems to be working fine to me.

main bison Feb 24, 2021, 7:36 AM

#

lean dome If there's a problem with duplicate pivots, I'm not seeing it.

what im seeing is that for every call it ads one value as the pivot and it sorts the rest to the right.

#

well.. i guess it will be cought in the right hand recursion

brisk saddle Feb 24, 2021, 7:37 AM

#

yeah, it will.

main bison Feb 24, 2021, 7:37 AM

#

and then empty sorted left..

brisk saddle Feb 24, 2021, 7:37 AM

#

left[:center] will go up before the pivot, while right[center:] will include the pivot, and everything else after.

lean dome Feb 24, 2021, 7:37 AM

#

Right. It chooses the pivot naively, and won't have the best possible performance, but it does sort correctly.

brisk saddle Feb 24, 2021, 7:37 AM

#

i am not looking to optimize performance (yet, of course).

#

but yeah, it does seem to work.

main bison Feb 24, 2021, 7:38 AM

#

i would just get all the pivots at once

#

and put them in the middle like your doing

#

since you already know where they should be

lean dome Feb 24, 2021, 7:38 AM

#

All the adjacent ones, you mean?

main bison Feb 24, 2021, 7:39 AM

#

if your pivot is 7

brisk saddle Feb 24, 2021, 7:39 AM

#

^^
is the issue with repeated pivots ones that come one after another, or just multiple occurrances of the same pivot?

main bison Feb 24, 2021, 7:39 AM

#

and you have five 7s in your list

#

when seven is picked as a pivot the first time, then you know that all the sevens should be in the middle

lean dome Feb 24, 2021, 7:39 AM

#

Ah, you mean with 3 lists and an if </elif ==/else.

main bison Feb 24, 2021, 7:39 AM

#

quicksort only sorts the pivot

#

so since it only sorts the pivot in the correct place, you should do that sort

brisk saddle Feb 24, 2021, 7:40 AM

#

oh you are right.

main bison Feb 24, 2021, 7:40 AM

#

yes, 3 lists

#

greater, equal, less

brisk saddle Feb 24, 2021, 7:40 AM

#

this seems more of a performance one, but if there are a lot of the same element than it would be a great increase to performance to just collect all of the same elements as the pivot before the actual sorting begins.

#

if i am interpreting what you said, correctly.

lean dome Feb 24, 2021, 7:42 AM

#

It's an interesting one. It speeds things up a lot in the case of many duplicate elements, but slows things down slightly in the case with all unique elements

main bison Feb 24, 2021, 7:42 AM

#

yes, creating lists is very slow

#

I mainly use quicksort as an example to teach recursion

brisk saddle Feb 24, 2021, 7:42 AM

#

i think i will still do what eivl suggests here, even if it will be a bit slower.

main bison Feb 24, 2021, 7:43 AM

#

not optimisation of quicksort

lean dome Feb 24, 2021, 7:43 AM

#

Overall, it's definitely a sensible optimization.

brisk saddle Feb 24, 2021, 7:43 AM

#

either way, thank you two very much for the suggested improvements.

main bison Feb 24, 2021, 7:43 AM

#

want me to share my version of it?

brisk saddle Feb 24, 2021, 7:43 AM

#

yeah sure.

main bison Feb 24, 2021, 7:43 AM

#

import random

def quick_sort(list_of_numbers):
    if len(list_of_numbers) <= 1:
        return list_of_numbers
    pivot = random.choice(list_of_numbers)

    less_then = [n for n in list_of_numbers if n < pivot]
    equal = [n for n in list_of_numbers if n == pivot]
    greater_then = [n for n in list_of_numbers if n > pivot]

    return quick_sort(less_then) + equal + quick_sort(greater_then)

brisk saddle Feb 24, 2021, 7:44 AM

#

list comprehension
that is genius

#

woah

#

alright cool, much appreciated either way.

main bison Feb 24, 2021, 7:45 AM

#

it also picks the pivot at random instead from the middle. but thats just a variant

lean dome Feb 24, 2021, 7:45 AM

#

Well... Comprehension is shorter for lines of code, but slower as well

brisk saddle Feb 24, 2021, 7:45 AM

#

oh right, i remember seeing that different ways of choosing the pivots have their own pros and cons.

#

i will also look into that tomorrow.

lean dome Feb 24, 2021, 7:45 AM

#

3 loops over the list is slower than 1 loop over it.

brisk saddle Feb 24, 2021, 7:45 AM

#

this is true

lean dome Feb 24, 2021, 7:45 AM

#

Slightly.

main bison Feb 24, 2021, 7:45 AM

#

yes, but it nicely showcases recursion

brisk saddle Feb 24, 2021, 7:46 AM

#

alright, well i will be heading to bed now.

#

have a nice sleep or morning, wherever you are.

main bison Feb 24, 2021, 7:46 AM

#

😄 morning here 😄

brisk saddle Feb 24, 2021, 7:46 AM

#

well, i hope you have a great morning!
goodnight, everyone.

lean dome Feb 24, 2021, 7:47 AM

#

I should go to bed too 😅

dapper sapphire Feb 24, 2021, 8:32 AM

#

Hi wondering if someone can look at the below implementation of the remove method for linked list and I also have few questions commented

    def remove(self, targetData):
        current = self.head
        previous = None
        found = False
        while(current != None):
            if(current.data == targetData):
                found = True
                break
            previous = current
            current = current.next
        if(found == True):
            if(previous == None):
                # So in this if statement we only have to do 1. Below are my comments
                self.head = current.next    # current.next is None
                self.head = None            # can we also do this?
                # So would either of the above be correct?
                
                # why cant we do the below? since current.next points None
                # why do we have to do self.head = current.next
                current = current.next
            else:
                previous.next = current.next

#

why cant we do:

            if(previous == None):
                current = current.next

When we do this it doesnt remove the last element

flat sorrel Feb 24, 2021, 8:38 AM

#

dapper sapphire Hi wondering if someone can look at the below implementation of the remove metho...

!e

a = [1, 2, 3]
b = a
b = [1, 2, 3, 4]

if a == [1, 2, 3, 4]:
    print("b = [1, 2, 3, 4] modified the value of a")
else:
    print("b = [1, 2, 3, 4] did not modify the value of a")

halcyon plankBOT Feb 24, 2021, 8:38 AM

#

@flat sorrel :white_check_mark: Your eval job has completed with return code 0.

b = [1, 2, 3, 4] did not modify the value of a

flat sorrel Feb 24, 2021, 8:40 AM

#

Similarly, the statement current = current.next doesn't change the object referred to by self.head. Instead, it causes current to reference current.next without doing anything to self.head.

dapper sapphire Feb 24, 2021, 9:00 AM

#

Oh ok, I see what you mean, current in that situation does not reference to self.head.

#

So we have to explicitly mention self.head and then point it to None.

sage berry Feb 24, 2021, 10:20 AM

#

i was wondering how i could make a basic text generator based on seeds

#

My inspiration: https://libraryofbabel.info/

Library of Babel

A project towards a universal library. By this art you may contemplate the variation of the 23 letters.

brisk saddle Feb 24, 2021, 1:13 PM

#

hey i remember that

#

@sage berry my first thought? a two-way/reversible hash algorithm.

#

actually, googling for "Reversible Hash Function" brings up a Quora post that brings up the Library of Babel.
https://www.quora.com/Are-there-any-reversible-hash-functions

#

now, do i know any that you could apply to your situation? no, but it might give you a better idea on how to go further.

#

if you do not know, a Reversible Hash Function is essentially just a Hash algorithm that can be, well, reversed, to get the original input.

#

the hash you initially generate would be the seed, and you can throw text through hashing algorithm to retrieve it's index in the sequence.

sage berry Feb 24, 2021, 1:18 PM

#

hash is a java term right? isnt it the equivalent of a dictionary in python?

#

or is it also some kind of encoder

brisk saddle Feb 24, 2021, 1:18 PM

#

Hashing is used in Hashtables/Hashmaps, but it is not exclusive to Java.

#

Hashing is when you take one input, and then turn it into something else. (bit of an oversimplification, i suppose.)

#

in the world of Computer Science this is often used to convert values to numbers, like in the case of a Hashtable, but this is certainly not the extent of the use.

#

so yeah, i guess you could say it is like an encoder, i suppose.

sage berry Feb 24, 2021, 1:21 PM

#

ok, so i need to make a reverseable encoder

brisk saddle Feb 24, 2021, 1:21 PM

#

yup!

#

now, how you do that is up to you, though.

there are one or two things that you need to look out for. for example, not only does your Hash algorithm have to be reversible, it will also have to be "perfect."

#

well, if you do not want collisions, i guess.

#

it does not have to be, but a non-perfect hash function can produce two values that return the same hash.

agile sundial Feb 24, 2021, 1:22 PM

#

hashing algorithms are meant to not be reversible

sage berry Feb 24, 2021, 1:22 PM

#

you mean i cant have 2 items be encoded to the same thing

brisk saddle Feb 24, 2021, 1:22 PM

#

they are not? 🤨

#

you certainly can, but i do not see why you would.

agile sundial Feb 24, 2021, 1:23 PM

#

how would reversing a hash even work

sage berry Feb 24, 2021, 1:23 PM

#

its an encoder not a 'hash'

brisk saddle Feb 24, 2021, 1:23 PM

#

good question, it is just an idea that came to mind.
sorry if i confused it with something else.

sage berry Feb 24, 2021, 1:24 PM

#

the first problem i run into is the encoding

#

if i have the seed set to 0

#

how do i take that and generate 410 pages or whatever

#

in your quora article it said something about a 273 bit hash

#

does that mean that the output is 273 bits

brisk saddle Feb 24, 2021, 1:25 PM

#

i mean, if you wanted to hash for example a string, and did so by adding up the ordinals of it's individual ASCII characters, you would need a way of extracting the individual ordinals out from the resulting number, i suppose.

agile sundial Feb 24, 2021, 1:26 PM

#

*happens to be very difficult

brisk saddle Feb 24, 2021, 1:26 PM

#

yes, so i guess if you wanted to "reverse" it you would somehow need to attach other information.

sage berry Feb 24, 2021, 1:26 PM

#

there has to be a way to decode stuff or else all of cryptography is a joke

agile sundial Feb 24, 2021, 1:26 PM

#

yes, it's encryption and decryption, not hashing

#

hashing is one way

brisk saddle Feb 24, 2021, 1:27 PM

#

ahh yes, that is the right term, sorry.

sage berry Feb 24, 2021, 1:27 PM

#

ok so we need to make an encryptor and decryptor

#

i not we

brisk saddle Feb 24, 2021, 1:28 PM

#

yeah, you do.

sage berry Feb 24, 2021, 1:29 PM

#

which should be simple? its supposed to be bad

brisk saddle Feb 24, 2021, 1:30 PM

#

i suppose it depends on how you plan on having your seed be represented.
entirely numerically? base-64?

sage berry Feb 24, 2021, 1:31 PM

#

yeah i think a base 10 seed of numbers

#

why do i need anything else

brisk saddle Feb 24, 2021, 1:31 PM

#

shrug, some people just choose other methods.

sage berry Feb 24, 2021, 1:32 PM

#

when someone says 256 bit encryption that means the encrypted message is always 256 bits

brisk saddle Feb 24, 2021, 1:32 PM

#

i believe so, yeah.

sage berry Feb 24, 2021, 1:34 PM

#

1 character is a byte right

agile sundial Feb 24, 2021, 1:34 PM

#

what do you mean by character?

brisk saddle Feb 24, 2021, 1:34 PM

#

not necessarily.

sage berry Feb 24, 2021, 1:35 PM

#

like 'a','b'

brisk saddle Feb 24, 2021, 1:35 PM

#

ASCII characters, yes.

agile sundial Feb 24, 2021, 1:35 PM

#

they are 2 bytes, i believe

brisk saddle Feb 24, 2021, 1:35 PM

#

if you include the extended table, it is one byte.

sage berry Feb 24, 2021, 1:35 PM

#

oh is the 265 bit encoded message a number that i convert into base 26 and use letters?

brisk saddle Feb 24, 2021, 1:35 PM

#

if you mean the standard table, it is 7 bits, but i think it is still stored in one byte.

#

i believe some Unicode characters are actually multi-bytes.

agile sundial Feb 24, 2021, 1:36 PM

#

yes

brisk saddle Feb 24, 2021, 1:37 PM

#

yeah, so if you intend to allow for Unicode, that might be a bit of an issue if you use UTF-8 as your encoding.

#

i might be wrong there, though.

sage berry Feb 24, 2021, 1:38 PM

#

then how do you decode 256 bits into more than 32 characters

brisk saddle Feb 24, 2021, 1:39 PM

#

that.. is a good question. frankly i am not educated enough in cryptography to answer.

sage berry Feb 24, 2021, 1:41 PM

#

maybe is does it in 32 character blocks

#

ok yeah they break down the message into blocks of 4 bytes or whatever

shut breach Feb 24, 2021, 7:21 PM

#

sage berry when someone says 256 bit encryption that means the encrypted message is always ...

it means the key is 256 bits

opaque spruce Feb 25, 2021, 5:31 AM

#

I'm confused

#

can someone help

opaque spruce Feb 25, 2021, 5:48 AM

#

im done already lmfao

dapper sapphire Feb 25, 2021, 6:53 AM

#

!e

print("How does this work??")

halcyon plankBOT Feb 25, 2021, 6:53 AM

#

You are not allowed to use that command here. Please use the #bot-commands channel instead.

dapper sapphire Feb 25, 2021, 6:58 AM

#

dapper sapphire !e ```python print("How does this work??") ```

!e

print("Test again")

halcyon plankBOT Feb 25, 2021, 6:58 AM

#

You are not allowed to use that command here. Please use the #bot-commands channel instead.

fickle seal Feb 25, 2021, 1:37 PM

#

Can anyone join my team in hashcode?
I have zero experience and no team pls help anyone

cloud moth Feb 25, 2021, 4:22 PM

#

do anyone know what data structures to look for building charts/graphs ?

carmine flare Feb 25, 2021, 4:24 PM

#

Think that depends on the chart and graph probably?

trim fiber Feb 25, 2021, 6:05 PM

#

No, what is this?

trim fiber Feb 25, 2021, 6:05 PM

#

cloud moth do anyone know what data structures to look for building charts/graphs ?

Lists looks okay for graphs

#

However you can use matrix if there are many edges between nodes

queen dagger Feb 25, 2021, 6:14 PM

#

Hey i'm learning data structures and algorithms for the first time and i'm documenting it. If your just learning them, you can follow along and even contribute if your interested https://github.com/jothamsl/Algorithms-n-Data-Structures

GitHub

jothamsl/Algorithms-n-Data-Structures

Python Data-Structures and Algorithms. Contribute to jothamsl/Algorithms-n-Data-Structures development by creating an account on GitHub.

cerulean wing Feb 25, 2021, 6:14 PM

#

found a course online, any feedback

#

https://sp21.datastructur.es/

Main | CS 61B Spring 2021

Computer Science 61B: Data Structures

brisk fox Feb 25, 2021, 7:26 PM

#

Create the following Application.

Use for loop, while loop, and do while loops to generate a table of decimal numbers,
as well as the binary, octal, and hexadecimal equivalents of the decimal numbers,
in the range 1-256.

The program should print the results to the Console without using any of the python conversion functions.
You must design and implement the necessary algorithms for the conversion.

Make sure to ready the requirements, ask question if not sure about the requirements.

Design Details:

The Main program should prompt the user for input.
A sample output is shown below.

Note:
To generate the binary numbers your code should use a while loop to generate
the binary numbers, a “for” loop to generate the octal numbers and a “do .. while” to
generate the hexadecimal numbers.

#

How do I do this?

#

I dont understand how the while loop is used to calculate the binary numbers

#

especially given that the numbers are a range

glass steeple Feb 25, 2021, 10:22 PM

#

not sure if this is more for this room or the data science room.i have a question about cleaning my csv data...i have this columns
Date,open,high,low,close,Volume BTC,Volume USDT,tradecount
2 0,2021-02-23 00:00:00,54087.67,54183.59,53405.5,53414.59,572.09326,30786788.62840657,16645.0

how do i clean the 0 column before 2021-02-23 but without cleaning the "date" header?

livid moss Feb 25, 2021, 11:57 PM

#

glass steeple not sure if this is more for this room or the data science room.i have a questio...

what do you mean by cleaning? what do you want to do with 0? drop the column?

runic stream Feb 26, 2021, 1:18 AM

#

Hard question for only the best data scientists haha: https://stackoverflow.com/questions/66378725/how-do-i-transfer-values-of-a-csv-files-between-certain-dates-to-another-csv-fil

Stack Overflow

How do I transfer values of a CSV files between certain dates to an...

Long question: I have two CSV files, one called SF1 which has quarterly data (only 4 times a year) with a datekey column, and one called DAILY which gives data every day. This is financial data so ...

livid moss Feb 26, 2021, 1:39 AM

#

runic stream Hard question for only the best data scientists haha: https://stackoverflow.com/...

Is that urs?

runic stream Feb 26, 2021, 1:58 AM

#

livid moss Is that urs?

yah. Trying to find an answer

#

I think I may have overcomplicated the question though

livid moss Feb 26, 2021, 2:12 AM

#

runic stream yah. Trying to find an answer

you want to merge the two csv file right?

runic stream Feb 26, 2021, 2:32 AM

#

livid moss you want to merge the two csv file right?

yes

cloud moth Feb 26, 2021, 2:40 AM

#

queen dagger Hey i'm learning data structures and algorithms for the first time and i'm docum...

nice comments in code.

brave oak Feb 26, 2021, 4:40 AM

#

runic stream Hard question for only the best data scientists haha: https://stackoverflow.com/...

this is a simple merge problem

#

just generate a join key for the second CSV based on the most recent date from the first CSV that is not later than the corresponding row’s date

#

then merge on that

mortal ravine Feb 26, 2021, 6:23 AM

#

I am having a problem that needs help in NLP.
The text "TSLA is going to the moon. I think TSLA is the greatest company ever and GM and other car manufacturers don't stand a chance when competing with TSLA" would ideally return something indicating that TSLA had positive sentiment and GM had negative sentiment.
How can I write a code in python?

fiery cosmos Feb 26, 2021, 2:23 PM

#

helllo

#

ciao

#

i quite the serveur

mint jewel Feb 26, 2021, 2:53 PM

#

for q in range(-s, s + 1):
    for r in range(-s, s + 1):
        if abs(q + r) <= s:
            print(q, r)
``` how would you write this such that the `if` isn't there. It isn't all that needed, since over half of the pairs are correct, but just out of curiosity.

uneven jungle Feb 26, 2021, 3:51 PM

#

@mint jewel sth like one Range from -s,0 and the other from 0,s

trim fiber Feb 26, 2021, 3:57 PM

#

Are you sure that it is {4} and {5} - not {3} and {4}?

#

"There is {0} and {1} but I do not like this {2}. I also know how to do {3} but {4} doesn't let me".format('apples', 'bananas', 'fruit', 'coding', 'someone')

#

!e

print("There is {0} and {1} but I do not like this {2}. I also know how to do {3} but {4} doesn't let me".format('apples', 'bananas', 'fruit', 'coding', 'someone'))

halcyon plankBOT Feb 26, 2021, 3:58 PM

#

You are not allowed to use that command here. Please use the #bot-commands channel instead.

trim fiber Feb 26, 2021, 4:14 PM

#

"There is {0} and {1} but I do not like this {2}. I also know how to do {3} but {4} doesn't let me".format(*data)

mortal ravine Feb 26, 2021, 5:03 PM

#

I am looking for help for my test assessment in NLP / sentiment analysis.
Task: The text "TSLA is going to the moon. I think TSLA is the greatest company ever and GM and other car manufacturers don't stand a chance when competing with TSLA" would ideally return something indicating that TSLA had positive sentiment and GM had negative sentiment.

karmic phoenix Feb 26, 2021, 5:11 PM

#

switching back and forth from c++ to python is a trip

#

its like speaking english and chinese bilingually to two people all day

#

if you dont do it in python theres a good chance you do it in c++ lmao

mint jewel Feb 26, 2021, 5:31 PM

#

uneven jungle <@207089259730042881> sth like one Range from -s,0 and the other from 0,s

how would that help?

uneven jungle Feb 26, 2021, 6:14 PM

#

@mint jewel Because s-s is <=s for all positive integers.

#

And 0

#

So you need to Only select negative s

#

In the ranges

mint jewel Feb 26, 2021, 6:19 PM

#

wouldn't that exclude that say 1 1?

runic stream Feb 26, 2021, 6:48 PM

#

brave oak just generate a join key for the second CSV based on the most recent date from t...

How would I do that?

uneven jungle Feb 26, 2021, 7:02 PM

#

1-1<1

#

At least this way you don't need the if.

brave oak Feb 27, 2021, 1:19 AM

#

@fervent saddle no like a tree dict

fervent saddle Feb 27, 2021, 1:20 AM

#

I’m thinking more about it, and maybe the trade off would actually be that you couldn’t delete from it at all

brave oak Feb 27, 2021, 1:20 AM

#

fervent saddle I’m thinking more about it, and maybe the trade off would actually be that you c...

why not

fervent saddle Feb 27, 2021, 1:21 AM

#

It might be complicated to update the hash array which points to insertion ordered array

#

But maybe I’m just not thinking about it hard enough

#

If you deleted, and then you moved everything back in the insertion ordered array, you would have to update the hashed into array so it didn’t direct to the wrong indexes

#

Well, no, maybe it would be fine. It would still be O(n), it would just be a longer O(n), I think

#

And it might need more space

#

Like everything in the insertion order array would need to hold what part of the hashed into array directs to it, or something like that

buoyant badger Feb 27, 2021, 1:25 AM

#

who can hop on a call and check this

vital compass Feb 27, 2021, 2:55 AM

#

if int(outlist[counter][0]) + 1 == int(z[0]) or int(outlist[counter][0]) - 1 == int(z[0]) or int(outlist[counter][1]) + 1 == int(z[1]) or int(outlist[counter][1]) - 1 == int(z[1]):

how do i check if this condition is met 3 timmes

brisk saddle Feb 27, 2021, 2:57 AM

#

why

#

have you heard of variables, lad?

#

that code is super messy and does not have to be that long.

#

also just store the result in an array, and then run the all function on said array.

dapper sapphire Feb 27, 2021, 3:20 AM

#

hahaha

#

You could probably use a counter if the statement is met and increment it to see if it ran 3 times at the end.

dapper sapphire Feb 27, 2021, 5:42 AM

#

So when we have

    def add(self, newData):
        newNodeAddress = Node(newData)
        newNodeAddress.next = self.head
        self.head = newNodeAddress

newNodeAddress.next is actually the memory address of the previous node
so when do add(1), add(2), add(3)

Below is what's happening. Of course we are dealing with memory address, but I used values to understand what's happening

add(1)
newNodeAddress.data = 1
newNodeAddress.next.data = self.head(None)
self.head = newNodeAddress.data(1)

add(2)
newNodeAddress.data = 2
newNodeAddress.next.data = self.head(1)
self.head = newNodeAddress.data(2)

add(3)
newNodeAddress.data = 3
newNodeAddress.next.data = self.head(2)
self.head = newNodeAddress.data(3)

#

And we assign self.head to newNodeAddress.next first, so we can keep track of the previous memory address

#

Because when we add 1, 2, 3
List will end up looking like 3, 2, 1, where:
self.head.data = 3
self.head.next.data = 2
self.head.next.next.data = 1
self.head.next.next.next = None # There's no data

nova holly Feb 27, 2021, 11:23 AM

#

guys O(n!) means that it grows very fast even if n is small

#

example:
1 --> 90
2 --> 890
3 --> 21345

#

right ?

jolly mortar Feb 27, 2021, 11:26 AM

#

yes, O(n!) grows very fast

pallid coral Feb 27, 2021, 12:31 PM

#

n!:
1 -> 1
2 -> 2
3 -> 6
4 -> 24
5 -> 120
6 -> 720
7 -> 5040
8 -> 40320
9 -> 362880

#

As you can see it gets bad really quickly

#

For an O(n!) operation on a list with 63 items, it would take 1982608315404440064116146708361898137544773690227268628106279599612729753600000000000000 operations

jolly mortar Feb 27, 2021, 1:06 PM

#

(minor correction: 2! is 2)

lament acorn Feb 27, 2021, 1:34 PM

#

How can we difference between the caracteres and the integers in python?

undone ingot Feb 27, 2021, 2:00 PM

#

How can you convert a string into a variable?

fair shell Feb 27, 2021, 2:26 PM

#

undone ingot How can you convert a string into a variable?

in python

var = 'string'
#if input is what you desire
var = input()
#to float it or turn it to an integer
float(var)
int(var)

undone ingot Feb 27, 2021, 2:52 PM

#

thx

#

I am getting a "unreacheable code" when I want to do more than 2 elif statesments

#

What can i do?

brave oak Feb 27, 2021, 3:01 PM

#

undone ingot I am getting a "unreacheable code" when I want to do more than 2 elif statesment...

show code

undone ingot Feb 27, 2021, 3:02 PM

#

@brave oak k = "name1n"

if k == "name":
print("hi")
elif "pter":
print("hi")
elif "d":
print("hi")

brave oak Feb 27, 2021, 3:02 PM

#

undone ingot <@171929073063297024> k = "name1n" if k == "name": print("hi") elif "pter":...

you want elif k == "pter":

undone ingot Feb 27, 2021, 3:02 PM

#

pycharm says to the last elif "The code is unreacheable

brave oak Feb 27, 2021, 3:02 PM

#

!e

print(bool("pter"))

halcyon plankBOT Feb 27, 2021, 3:02 PM

#

@brave oak :white_check_mark: Your eval job has completed with return code 0.

True

sleek pendant Feb 27, 2021, 3:03 PM

#

My PC from 1 million coinflips throw 16k, 6 streaks

#

https://gist.github.com/enkeyz/23e3d6314a76b5ff26a3c43560f73e15

undone ingot Feb 27, 2021, 3:27 PM

#

@brave oak but when want to print it at the end i doesn't work

#

@brave oak the variable k

hushed rock Feb 27, 2021, 5:15 PM

#

Hey, I have a question.
I want to make a class that helps with encrypted files for my project in a way that you can decrypt it with a key and edit the content only (the file is supposed to contain a 512bit salt at the beginning and content comes right after it).
Any way to make it work like a buffered reader or BytesIO?
BytesIO(file.read()) will not work because it takes a very long time to get a large file...

Thanks in advance!

dapper sapphire Feb 27, 2021, 6:08 PM

#

hushed rock Hey, I have a question. I want to make a class that helps with encrypted files f...

I havent done a project on encryption and decryption, but I did a project on hashing(md5, and sha2) and recoded part of openssl which I suppose has a similar concept, but you just cant decrypt it. But the code I wrote took longer to run on big files, but the original openssl created a hash pretty much right away even for big files. So I would say if there's an open source project that's doing something similar to what you are doing and that project runs fast then maybe look at the source code and see how they optimized it.

dapper sapphire Feb 27, 2021, 6:25 PM

#

What's the size of your buffer right now?

#

I think increasing the buffer size or chunk size when you stream data might work.

hushed rock Feb 27, 2021, 6:28 PM

#

currently my buffer is 32k

dapper sapphire Feb 27, 2021, 6:28 PM

#

32,000?

hushed rock Feb 27, 2021, 6:28 PM

#

yeah

#

but like... kb

dapper sapphire Feb 27, 2021, 6:29 PM

#

Yeah, and how big is the file you are working with is it in GB?

hushed rock Feb 27, 2021, 6:29 PM

#

I'm testing it on a 6GB file which takes about 5 sec to read whole

dapper sapphire Feb 27, 2021, 6:30 PM

#

Maybe try increasing the buffer from 32k to 64k and see if it takes less time.

hushed rock Feb 27, 2021, 6:33 PM

#

maybe, ima try that rq

#

huh... although i think that happen because this time i ran the code on an hdd

#

also seconds not ms

dapper sapphire Feb 27, 2021, 6:36 PM

#

Yeah run it on the same drive you were previously running it on that gave you 5 seconds with 32k buffer.

#

hdd would be slow.

hushed rock Feb 27, 2021, 6:37 PM

#

yeah much better

#

welp i think this'll be fast enough for me, I'm not expecting larger than 20gig files

dapper sapphire Feb 27, 2021, 6:40 PM

#

Nice! And you probably already know the trade off of doubling the buffer size.

hushed rock Feb 27, 2021, 6:40 PM

#

yeah lmao
thanks!

dapper sapphire Feb 27, 2021, 6:42 PM

#

Wondering if someone could comment on my though process of adding an element to a linked list:
#algos-and-data-structs message
#algos-and-data-structs message

brisk saddle Feb 27, 2021, 6:47 PM

#

can tombstones in Hashtables be overwritten, or must they remain until the next rehash?

nova holly Feb 27, 2021, 6:58 PM

#

pallid coral n!: 1 -> 1 2 -> 2 3 -> 6 4 -> 24 5 -> 120 6 -> 720 7 -> 5040 8 -> 40320 9 -> 362...

thx for ur help

kindred whale Feb 27, 2021, 9:45 PM

#

How can I insert a node after a prev_node in a Linked List, so basically the input of the function is

def insert_value(self, prev_node, new_value):

brisk saddle Feb 27, 2021, 10:00 PM

#

save the next_node of prev_node in a variable.

#

then, set the next_node of prev_node to Node(new_value) (or however you initialize a Node)

shut dragon Feb 27, 2021, 10:00 PM

#

hello

brisk saddle Feb 27, 2021, 10:00 PM

#

then, set the next_node of that new node to the node you saved in a variable.

#

greetings, friend.

shut dragon Feb 27, 2021, 10:01 PM

#

pip install pyaudio
File "<stdin>", line 1
pip install pyaudio
^
SyntaxError: invalid syntax

brisk saddle Feb 27, 2021, 10:01 PM

#

this is a channel for algorithms and datastructures.

shut dragon Feb 27, 2021, 10:01 PM

#

Greetings

brisk saddle Feb 27, 2021, 10:01 PM

#

you need to run that command in your shell, not the Python interpreter.

shut dragon Feb 27, 2021, 10:02 PM

#

how can I do it

brisk saddle Feb 27, 2021, 10:03 PM

#

by executing it in your shell. open your terminal and type that command. you are running it in Python, which is the wrong place.

shut dragon Feb 27, 2021, 10:05 PM

#

Thank you so much, I'm doing artificial intelligence.

brisk saddle Feb 27, 2021, 10:06 PM

#

good luck!

shut dragon Feb 27, 2021, 10:06 PM

#

thanks

brisk saddle Feb 27, 2021, 10:09 PM

#

no problem.

kindred whale Feb 27, 2021, 10:53 PM

#

brisk saddle save the ``next_node`` of ``prev_node`` in a variable.

thank you

brisk saddle Feb 27, 2021, 10:53 PM

#

anytime.

sudden rover Feb 28, 2021, 3:39 AM

#

#

but its already on

#

microsoft store aaps does not work

#

can anyone help

night plank Feb 28, 2021, 11:06 AM

#

hello everyone

#

i got a question about newtwon raphson algorithm

#

can someone help me with this equation pls

#

https://paste.pythondiscord.com/dufemejina.apache

topaz pulsar Feb 28, 2021, 2:02 PM

#

you don't define epsilon anywhere, you also need to indent the relevant part below the while loop so that it is included in that loop

old rover Feb 28, 2021, 4:57 PM

#

hi everyone i'm a noob to big O

#

x = 5 + (15*20)
y = 15 -2
print(x+y)

#

can someone please explain why constants are O(1)?

mint jewel Feb 28, 2021, 5:00 PM

#

if the duration is independent of some input size, then it is constant

old rover Feb 28, 2021, 5:00 PM

#

so any equation with constants is just O(1)

mint jewel Feb 28, 2021, 5:01 PM

#

yes, 1 + 1 will take equally long regardless of what input you have, since it doesn't use the input in any way

old rover Feb 28, 2021, 5:02 PM

#

uhhhh should i be learning this before i learn recursion and polymorphism?

agile sundial Feb 28, 2021, 5:02 PM

#

time complexity?

old rover Feb 28, 2021, 5:02 PM

#

yes

jolly mortar Feb 28, 2021, 5:02 PM

#

you should tbh, it's usually intuitive any way

old rover Feb 28, 2021, 5:03 PM

#

isn't recursion when a function calls itself

#

never used it before

jolly mortar Feb 28, 2021, 5:03 PM

#

old rover isn't recursion when a function calls itself

yep

prisma moth Feb 28, 2021, 5:03 PM

#

The total number of steps T(n) wouldn't be T(1) but O() abstracts constant factors and only keeps the most important factor

old rover Feb 28, 2021, 5:04 PM

#

why is a for loop big O(n)

#

sorry i'm asking noob questions

#

learning this for the first time

mint jewel Feb 28, 2021, 5:04 PM

#

because looping over 500 elements is twice as fast as looping over a 1000 elements

#

the time it takes is linear to the amount of elements

jolly mortar Feb 28, 2021, 5:05 PM

#

yeah

mint jewel Feb 28, 2021, 5:05 PM

#

now, this is not true for every for loop

jolly mortar Feb 28, 2021, 5:05 PM

#

if there was another loop within the outer loop, which is iterating over the list again, you'd get a O(n^2)

#

like

for i in my_list:
  for j in my_list:
    print(i == j)

for each item in the list, it has to go through the entire list again

old rover Feb 28, 2021, 5:07 PM

#

is there a book that just teaches big O(n)? simply?

agile sundial Feb 28, 2021, 5:07 PM

#

i doubt you'd find a book with only big O, but any algos text will have something on it

peak wagon Feb 28, 2021, 5:07 PM

#

#

Might help to visualize it

old rover Feb 28, 2021, 5:07 PM

#

i'll watch some more videos and keep asking questions

#

If you've never covered big O in an academic setting, you can probably skip this subsection. It might confuse you more than it helps. This "FYI" is mostly here to clear up ambiguity in wording for people who have learned big O before, so that they don't say, "But I thought big O meant..:'

agile sundial Feb 28, 2021, 5:09 PM

#

that's from a book...?

old rover Feb 28, 2021, 5:10 PM

#

cracking the coding interview

#

some edition that I ~~borrowed~~

jolly mortar Feb 28, 2021, 5:10 PM

#

pick another book which does explain big O ¯_(ツ)_/¯

old rover Feb 28, 2021, 5:10 PM

#

yeah i think there has to be one

#

um

agile sundial Feb 28, 2021, 5:10 PM

#

CLRS introduction to algorithms

old rover Feb 28, 2021, 5:10 PM

#

do i have to reteach myself calculus to learn big o

#

is that a thing

raw zealot Feb 28, 2021, 5:10 PM

#

Guys, there is an interview ques
if you are given some coordinatesFind the number of rectangles which can be formed,What's the key to start coding regarding this prompt

#

Like coordinates on a Cartesian plane

#

6-8

#

We have to find all the possible rectangle we can frame using any 4

#

This is a Google interview ques 👀

old rover Feb 28, 2021, 5:12 PM

#

that looks like an interview question for FAANG

#

damn beat me to the punch

raw zealot Feb 28, 2021, 5:12 PM

#

Yesh

#

Baang for faang

old rover Feb 28, 2021, 5:12 PM

#

but it's also a question that startups have started asking too

#

every company wants to be FAANG

#

sorry didn't want to go off on a rant

mint jewel Feb 28, 2021, 5:12 PM

#

I think you can do this with set intersections

#

but I am not quite sure

old rover Feb 28, 2021, 5:13 PM

#

so if you have a nested for loop it's O(N^2)?

#

that actually makes sense

prisma moth Feb 28, 2021, 5:13 PM

#

An O(n^2) algorithm will always be worse than an O(n) in the long run but if the two algorithms are T(n^2 + 1) and T(100n + 1000), then the O(n^2) algorithm is actually better for n < 100

jolly mortar Feb 28, 2021, 5:14 PM

#

old rover yeah i think there has to be one

mind if I DM you a book?

raw zealot Feb 28, 2021, 5:14 PM

#

mint jewel I think you can do this with set intersections

🤔 intersection function seems complicated

old rover Feb 28, 2021, 5:14 PM

#

jolly mortar mind if I DM you a book?

ofc anything is appreciated

mint jewel Feb 28, 2021, 5:14 PM

#

do the rectangles have to be axis aligned?

raw zealot Feb 28, 2021, 5:14 PM

#

Yes

#

Parallel to the axis

#

Like

.         .            .

.         .            .

agile sundial Feb 28, 2021, 5:15 PM

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old rover do i have to reteach myself calculus to learn big o

not really

raw zealot Feb 28, 2021, 5:15 PM

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These are the points through which 3 rectangles could be formed

mint jewel Feb 28, 2021, 5:15 PM

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then you can find all points with common X coordinates and all points with common Y coordinates, and then there is some clever way to do the intersection such that you get all the points

raw zealot Feb 28, 2021, 5:16 PM

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Hm

agile sundial Feb 28, 2021, 5:16 PM

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if n is small just brute force 😔

raw zealot Feb 28, 2021, 5:16 PM

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We need to find the combinations

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for all 3 rectangle

raw zealot Feb 28, 2021, 5:16 PM

#

raw zealot Like ```py . . . . . . ```

In case of this

old rover Feb 28, 2021, 5:16 PM

#

agile sundial not really

good shit

mint jewel Feb 28, 2021, 5:16 PM

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ye, nothing wrong with a good ole

for a, b, c, d in combinations(points, 4)

agile sundial Feb 28, 2021, 5:16 PM

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lul

raw zealot Feb 28, 2021, 5:17 PM

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Will try this soon

mint jewel Feb 28, 2021, 5:17 PM

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actually, what is the big O of choose k

uneven jungle Feb 28, 2021, 5:18 PM

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Question: does this have a particular name? It's not fully regular bubble-sort.

raw zealot Feb 28, 2021, 5:18 PM

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Wut

mint jewel Feb 28, 2021, 5:23 PM

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well, it is wrong regardless. It can easily go into n < 0@uneven jungle

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and well, n < -len(S)

old rover Feb 28, 2021, 5:26 PM

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what does "worst-case scenario" even mean?

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"What if we get really unlucky and the pivot is repeatedly the biggest element in the array?"

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what's a pivot? never heard that term before

agile sundial Feb 28, 2021, 5:27 PM

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quicksort?

mint jewel Feb 28, 2021, 5:27 PM

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consider bubble sort. Best case scenario is that the list is already sorted, so you don't have to actually swap anything

old rover Feb 28, 2021, 5:27 PM

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are you guys talking to me?

mint jewel Feb 28, 2021, 5:27 PM

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worst case is if it sorted, but in the wrong direction IIRC

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yes

agile sundial Feb 28, 2021, 5:27 PM

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for bubble sort yeah, reverse sorted is worst case

old rover Feb 28, 2021, 5:28 PM

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idk what quicksort or bubblesort even is

mint jewel Feb 28, 2021, 5:28 PM

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oh

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then lets make a simpler example

agile sundial Feb 28, 2021, 5:28 PM

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you're in the sorting algos section of your book right?

old rover Feb 28, 2021, 5:28 PM

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i'm in the big o notation section of cracking the coding interview

agile sundial Feb 28, 2021, 5:28 PM

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oh damn, they assume you know a bunch of stuff

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maybe start with a more introductoory book then

old rover Feb 28, 2021, 5:28 PM

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"O (big 0): In academia, big O describes an upper bound on the time. An algorithm that prints all the values in an array could be described as O(N), but it could also be described as O(N2), O(N3), or 0(2N) (or many other big O times). The algorithm is at least as fast as each of these; therefore they are upper bounds on the runtime. This is similar to a less-than-or-equal-to relationship. If Bob is X years old (I'll assume no one lives past age 130), then you could say X .$. 130. It would also be correct to say that X .$. 1, 000 or X .$. 1,000,000. It's technically true (although not terribly useful). Likewise, a simple algorithm to print the values in an array is O(N) as well as O(N3 ) or any runtime bigger than O(N)."

#

this is like the first paragraph they even show about big O

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ok cracking the coding interview is overrated

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for beginners yes

prisma moth Feb 28, 2021, 5:31 PM

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Worst case scenario is the max number of operations required

old rover Feb 28, 2021, 5:32 PM

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constants matter if the input size is small

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got it

mint jewel Feb 28, 2021, 5:33 PM

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in which case, big O doesn't

uneven jungle Feb 28, 2021, 5:33 PM

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mint jewel well, it is wrong regardless. It can easily go into n < 0<@!427336660305313802>

even if it might use some negative n's it still works

agile sundial Feb 28, 2021, 5:34 PM

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you tested that?

mint jewel Feb 28, 2021, 5:34 PM

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I tested it and it spat an index error at me.

#

In [33]: S = [random.random() for _ in range(100)]

In [34]: l = len(S) - 1
    ...: n = 0
    ...: while n < l:
    ...:     if S[n] > S[n+1]:
    ...:         S[n], S[n+1] = S[n+1], S[n]
    ...:         n -= 1
    ...:     else:
    ...:         n += 1
    ...:
---------------------------------------------------------------------------
IndexError                                
      2 n = 0
      3 while n < l:
----> 4     if S[n] > S[n+1]:
      5         S[n], S[n+1] = S[n+1], S[n]
      6         n -= 1

IndexError: list index out of range

old rover Feb 28, 2021, 5:35 PM

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uhhhhhh

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there has to be something that can explain big O to my beginner ass

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https://youtu.be/v4cd1O4zkGw

YouTube

HackerRank

Big O Notation

Learn about Big O notation, an equation that describes how the run time scales with respect to some input variables. This video is a part of HackerRank's Cracking The Coding Interview Tutorial with Gayle Laakmann McDowell. http://www.hackerrank.com/domains/tutorials/cracking-the-coding-interview?utm_source=video&utm_medium=youtube&utm_campaign=ctci

▶ Play video

#

trying this one

agile sundial Feb 28, 2021, 5:37 PM

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clrs algorithms is more introductory for algorithms in general

old rover Feb 28, 2021, 5:38 PM

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agile sundial clrs algorithms is more introductory for algorithms in general

i will check it out thanks for being so helpful and supportive

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you would recommend the third edition right?

agile sundial Feb 28, 2021, 5:38 PM

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¯_(ツ)_/¯

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whichever yuo can get is fine

old rover Feb 28, 2021, 5:39 PM

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whatever i found it in the third edition so i'm using it in the third edition i don't know why i asked

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thanks for suggesting it

uneven jungle Feb 28, 2021, 5:40 PM

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mint jewel I tested it and it spat an index error at me.

wierd, it passes my test.

mint jewel Feb 28, 2021, 5:41 PM

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it does work on some arrays

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but not on all of them

agile sundial Feb 28, 2021, 5:41 PM

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!e

from random import random
L = [random() for _ in range(200)]
n = 0
l = len(L) - 1
while n < l:
  if L[n] > L[n + 1]:
    L[n], L[n + 1] = L[n + 1], L[n]
    n-= 1
  else:
    n += 1

halcyon plankBOT Feb 28, 2021, 5:41 PM

#

@agile sundial :x: Your eval job has completed with return code 1.

001 | Traceback (most recent call last):
002 |   File "<string>", line 6, in <module>
003 | IndexError: list index out of range

mint jewel Feb 28, 2021, 5:42 PM

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you may want to look into parametric tests

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such as hypothesis

old rover Feb 28, 2021, 5:44 PM

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what if you had a lawn of grass that's 100 by 100 and you had to mow it all

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what's the runtime???

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that sounds like a FAANG question to me

raw zealot Feb 28, 2021, 5:45 PM

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Wut

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Thats not enough data

old rover Feb 28, 2021, 5:45 PM

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the question?

raw zealot Feb 28, 2021, 5:45 PM

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Yes

mint jewel Feb 28, 2021, 5:45 PM

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you can determine complexity on things that have some number or numbers which describe its input

old rover Feb 28, 2021, 5:46 PM

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oh it's a square

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does that help

mint jewel Feb 28, 2021, 5:46 PM

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you didn't say what is the number that changes here

old rover Feb 28, 2021, 5:46 PM

#

https://youtu.be/v4cd1O4zkGw?t=210

YouTube

HackerRank

Big O Notation

Learn about Big O notation, an equation that describes how the run time scales with respect to some input variables. This video is a part of HackerRank's Cracking The Coding Interview Tutorial with Gayle Laakmann McDowell. http://www.hackerrank.com/domains/tutorials/cracking-the-coding-interview?utm_source=video&utm_medium=youtube&utm_campaign=ctci

▶ Play video

#

check it out if you have time

#

the number that changes???

agile sundial Feb 28, 2021, 5:47 PM

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big O is an expression that describes how the runtime changes when you change the input size

raw zealot Feb 28, 2021, 5:47 PM

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The time for mowing a single grass should be given

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👀

old rover Feb 28, 2021, 5:47 PM

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well it's cracking the coding interview

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she can't even explain big O notation without assuming you already know stuff

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if you can't explain topics to me like a 5 year old i'm not reading the book sorry

raw zealot Feb 28, 2021, 5:48 PM

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HMM

old rover Feb 28, 2021, 5:48 PM

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the 5 year old strategy is from TAs at my college

mint jewel Feb 28, 2021, 5:48 PM

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lets actually state a good question

what is time complexity of mowing a square lawn with a side of N

old rover Feb 28, 2021, 5:48 PM

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mint jewel lets actually state a good question ``` what is time complexity of mowing a squa...

that is better but i don't know how to answer that either

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she said it's O(a) and a is the area of grass

mint jewel Feb 28, 2021, 5:48 PM

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think about how does the amount of work scale in relation to N

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that is correct

old rover Feb 28, 2021, 5:49 PM

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or it's O(s^2) which is the length on one side

mint jewel Feb 28, 2021, 5:49 PM

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that is also correct

old rover Feb 28, 2021, 5:49 PM

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but how did she even figure that out

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well it's square so

mint jewel Feb 28, 2021, 5:49 PM

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well, how much longer does it take to mow 100 Ares than 50 Ares

old rover Feb 28, 2021, 5:50 PM

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100*100 v 50 *50?

mint jewel Feb 28, 2021, 5:50 PM

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an Are is a unit of area

agile sundial Feb 28, 2021, 5:50 PM

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old rover she can't even explain big O notation without assuming you already know stuff

i mean, algorithms are not a beginner topic. you kinda have to assume your audience understands basic programming topics

old rover Feb 28, 2021, 5:50 PM

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agile sundial i mean, algorithms are not a beginner topic. you kinda have to assume your audie...

i do understand basic programming topics...... I think

raw zealot Feb 28, 2021, 5:51 PM

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mint jewel an Are is a unit of area

Acre?

old rover Feb 28, 2021, 5:51 PM

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i know all the stuff in automate the boring stuff

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~~but i can't do hackerrank problems~~

mint jewel Feb 28, 2021, 5:51 PM

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Are is also correct

uneven jungle Feb 28, 2021, 5:51 PM

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@old rover then you only have the fun left, good for you

mint jewel Feb 28, 2021, 5:51 PM

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acre is not a metric unit

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Are is 100 sq. m.

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how is this unit so obscure

old rover Feb 28, 2021, 5:52 PM

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uneven jungle <@!567030124306759710> then you only have the fun left, good for you

is this sarcasm? i detect sarcasm

mint jewel Feb 28, 2021, 5:52 PM

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alright, new question

#

how much longer does it take to mow 1000 square meters than 500 square meters

old rover Feb 28, 2021, 5:52 PM

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i can't upload images here right?

mint jewel Feb 28, 2021, 5:52 PM

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you can

old rover Feb 28, 2021, 5:52 PM

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ok hang on

mint jewel Feb 28, 2021, 5:52 PM

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at least I think so

raw zealot Feb 28, 2021, 5:53 PM

#

#

👀

old rover Feb 28, 2021, 5:53 PM

#

#

this is in C++? or C? or C#? idk

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but why is it O(a*b) instead of O(N^2)

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bc of the inputs???

mint jewel Feb 28, 2021, 5:54 PM

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well, what would be N in O(N^2)

raw zealot Feb 28, 2021, 5:54 PM

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I guess cpp

mint jewel Feb 28, 2021, 5:54 PM

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that is pseudocode probably

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cpp doesn't have for in

old rover Feb 28, 2021, 5:54 PM

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yeah i think it's psuedocode

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it probably is

raw zealot Feb 28, 2021, 5:54 PM

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Yee, I have seen it , too many curly brackets {}{}} in a pseudocode

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Like Google interviews

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Lol 👀

old rover Feb 28, 2021, 5:55 PM

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google interviews got every damn company thinking they're google

#

anyways i still don't get why it's O(a*b)

mint jewel Feb 28, 2021, 5:55 PM

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well, what do you think it is?

old rover Feb 28, 2021, 5:56 PM

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i don't think it's O(N^2) bc it's not a nested for loop

raw zealot Feb 28, 2021, 5:56 PM

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🤓 aight , see u guys after understanding data structures

old rover Feb 28, 2021, 5:56 PM

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peace out dude

raw zealot Feb 28, 2021, 5:56 PM

#

Bai

agile sundial Feb 28, 2021, 5:56 PM

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there is a for loop inside of a for loop

old rover Feb 28, 2021, 5:56 PM

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ok then i don't get it at all

raw zealot Feb 28, 2021, 5:56 PM

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Double loop

#

O(a*b) 🤔

old rover Feb 28, 2021, 5:57 PM

#

O(a*b)

raw zealot Feb 28, 2021, 5:57 PM

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Looking like a func

#

Lol

mint jewel Feb 28, 2021, 5:58 PM

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well, you have 2 inputs

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both of which affect the time

#

so the O obviously has to respect both

old rover Feb 28, 2021, 5:58 PM

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uhhhhh

#

ok

raw zealot Feb 28, 2021, 5:58 PM

#

What actually

#

Is

#

O

old rover Feb 28, 2021, 5:59 PM

#

good question

mint jewel Feb 28, 2021, 5:59 PM

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big O notation is a way to describe how expensive something is for really large inputs

old rover Feb 28, 2021, 5:59 PM

#

raw zealot O

In academia, big O describes an upper bound on the time. An algorithm that prints all the values in an array could be described as O(N), but it could also be described as O(N2), O(N3), or 0(2N) (or many other big O times). The algorithm is at least as fast as each of these; therefore they are upper bounds on the runtime. This is similar to a less-than-or-equal-to relationship. If Bob is X years old (I'll assume no one lives past age 130), then you could say X .$. 130. It would also be correct to say that X .$. 1, 000 or X .$. 1,000,000. It's technically true (although not terribly useful). Likewise, a simple algorithm to print the values in an array is O(N) as well as O(N3 ) or any runtime bigger than O(N).

mint jewel Feb 28, 2021, 5:59 PM

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its not as useful as people try to make you believe

old rover Feb 28, 2021, 5:59 PM

#

there you go that's straight from cracking the coding interierw

raw zealot Feb 28, 2021, 5:59 PM

#

Clipboard huh

old rover Feb 28, 2021, 5:59 PM

#

i am gonna use that giant wall of text every time someone asks

#

kidding

old rover Feb 28, 2021, 6:00 PM

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mint jewel its not as useful as people try to make you believe

you're right, but you're supposed to show off how smart you are to interviewers by talking about this

#algos-and-data-structs

packageInfo.bash

Purpose: Generates a report to displaying specified information of installed software

USAGE: ./packageInfo.bash [application-name]

Author: *** INSERT YOUR NAME ***

Date: *** CURRENT DATE ***

Create report title (echo with -e option allows newline \n character to be used)

Clear screen and use Here Document to display select on report items to read into variable

Convert spaces to pipe symbol (|)

Use sed with extended regular expressions to only print those matching report elements

Author: * INSERT YOUR NAME *

Date: * CURRENT DATE *