any tips on how i can learn a linked List (data structure)

[distant wraith]

<@&987246399047479336> please have a look, thanks.

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TJ-Bot

Help please

To learn about linked lists in Java, there are a few steps you can take:

1. Understand the basics: A linked list is a data structure consisting of nodes where each node contains data and a reference to the next node in the sequence. It does not have a fixed size like arrays.

2. Study Java LinkedList class: Start by familiarizing yourself with the LinkedList class in Java, which is an implementation of a doubly-linked list. Look at the methods available such as add(), remove(), get(), and more.

3. Implement your own linked list: Practice implementing your own version of a linked list from scratch. This will help you understand how nodes are created, connected, and manipulated within the list.

4. Solve problems using linked lists: Practice solving coding problems that involve linked lists to solidify your understanding. Websites like LeetCode or HackerRank offer a variety of problems to work on.

5. Seek resources and tutorials: There are plenty of online resources, tutorials, and videos available that can help you learn more about linked lists in Java. Utilize these to enhance your understanding.

6. Ask for help: Don't hesitate to reach out to communities like this Discord server for help if you get stuck or have any questions about linked lists in Java.

By following these steps, you'll be well on your way to mastering linked lists in Java!

- AI generated response

[spark onyx]

okay so for context

this is a very common starter assignment

and its very often given well before you are able to do it easily

there are a few ways of teaching linked lists that aren't bad, but they require your curriculum to be a little special (you needed to learn interfaces)

but its obviously not impossible to grasp

the key property of a linked list is that it is either

• empty
• not empty

the way your teacher probably wants you to represent it is with a Node class

Node node = null;

if the Node is null that means it is empty

if the node is not null it is not empty

class Node {
    int head;
    Node tail;
}

when a linked list is not empty it means you have at least one piece of data

in this case lets assume all the data is in ints so you have some int at the "head" of the list

the "tail" is another Node

and thus might be empty or not empty itself

@cosmic hemlock Taking a break, ask questions now and i'll continue

[cosmic hemlock]

okay so the way i started doing it is like this

class Node {
Node next;

int data

[spark onyx]

yeah next/data, head/tail, first/rest

take your pick

[cosmic hemlock]

public Node(int data) {
this.data = data;
this.next = null;
}
}

[spark onyx]

okay lets pause

[cosmic hemlock]

alrighrt yea sure

[spark onyx]

so writing that here

class Node {
    int head;
    Node tail;

    Node(int head) {
        this.head = head;
        this.tail = null;
    }
}

if you were to say new Node(5) then head will be 5 and tail will be null

this means it will be a linked list with one element

so not empty -> empty

does that track?

[cosmic hemlock]

yea so first node will be pointed as head and tail

[spark onyx]

err

[cosmic hemlock]

since there is only one element

[spark onyx]

lets use our words

[cosmic hemlock]

or number

[spark onyx]

what does "pointed as head and tail" mean

[cosmic hemlock]

since there is only one element the tail and head will point to that number since its only one

[spark onyx]

no

there is only one element

the first node has that element at the head

and it points to a null or empty tail

you aren't wrong but i really want to make sure we are specific with language

okay so

a change I will make

class Node {
    int head;
    Node tail;

    Node(int head, Node tail) {
        this.head = head;
        this.tail = tail;
    }
}

lets add the tail to the constructor

[cosmic hemlock]

sorry if i sound silly its been only a month for me

[spark onyx]

we can have more than one constructor, but its easier to focus in

[cosmic hemlock]

okay tail

[spark onyx]

so now lets say I did this

new Node(1, new Node(2, null));

this goes

not empty (1) -> not empty (2) -> empty

[cosmic hemlock]

1, new Node

2, null

[spark onyx]

yep

okay so next change we will make, it might feel pointless

we are going to mark head and tail as final

class Node {
    final int head;
    final Node tail;

    Node(int head, Node tail) {
        this.head = head;
        this.tail = tail;
    }
}

this means that after we make a Node, the values in there won't change

it doesn't do anything other than make it so that if you try to do this

Node n = new Node(1, null);
n.head = 6;

Java won't let you

this is just to stop you from making some common mistakes and getting confused

[cosmic hemlock]

will we make a append method prepend method and delete method and print method

[spark onyx]

sure

lets start with append

what should append take as arguments?

[cosmic hemlock]

int data

or

head

[spark onyx]

so the next part is made a little annoying by the choice to use null as empty

but

class Node {
    final int head;
    final Node tail;

    Node(int head, Node tail) {
        this.head = head;
        this.tail = tail;
    }

    static Node append(Node list, int data) {
         // ...
    }
}

now lets address the fact that it is static

normally, java lets you call methods on objects like this

[cosmic hemlock]

this looks more complicated

i usually just create another class linkedlist

[spark onyx]

i understand

hold with me

[cosmic hemlock]

holding

[spark onyx]

String s = "abc";
int len = s.length();

so in this code, what will the value of len be

not a trick question

[cosmic hemlock]

2\\\\\\\\

[spark onyx]

abc

1 2 3

3

its 3

[cosmic hemlock]

oh

for strings

it doesnt do that right

[spark onyx]

its not indexing

[cosmic hemlock]

oh this is lenght

sorry sorry

[spark onyx]

its just telling you the length

okay so now

String s = "";
int len = s.length();

what will len be

[cosmic hemlock]

null

[spark onyx]

0

it has zero characters

[cosmic hemlock]

or garabe

garabge

okay oay

[spark onyx]

nope, well defined

its just 0

now what will len be

String s = null;
int len = s.length();

[cosmic hemlock]

nullllllllllllllllll

[spark onyx]

nope

it will crash

if you try to do something like .length() and the thing on the left is null, you get a crash

[cosmic hemlock]

rage quit

[spark onyx]

it has no feelings but sure

class Node {
    final int head;
    final Node tail;

    Node(int head, Node tail) {
        this.head = head;
        this.tail = tail;
    }

    static Node append(Node list, int data) {
         // ...
    }
}

so now here

the reason we take in the node as an argument

and the reason it is static

is because we have that whole "empty is represented by null" thing

if you tried node.append(5) and node was null, it would crash

sorta make sense?

[distant wraith]

I uploaded your attachments as Gist.

[spark onyx]

don't share your code

[cosmic hemlock]

but this is alot easier

[spark onyx]

we are doing it from scratch

[cosmic hemlock]

yea but the way your doing it is way out of my understanding

like im pretty new new

[spark onyx]

your way of doing it is way out of your understanding

everything is out of your understanding

[cosmic hemlock]

no its from my professor

[spark onyx]

thats why we are going through this

if you want your professor to teach you you should reach out to him

if you want me to teach you follow my instructions

[cosmic hemlock]

yea but instructions should be understandable

you dont skip a few steps

yk

you go from easy to hard

not hard then easy

its better for people to understand that way

[mortal valley]

do you understand the concept of "linked"?

[cosmic hemlock]

yea

[spark onyx]

im out

[cosmic hemlock]

but when it comes to the coding part i kinda get lost

with all the this == this

this = this

[mortal valley]

do you understand how classes work?

[cosmic hemlock]

if this blah blah

yea

[bitter thicket]

u get lost bc u skipped a hand full of steps

[cosmic hemlock]

i would be eaiser if there was a class

[bitter thicket]

and are packing practice with these steps

[spark onyx]

(steps which I am trying to make you do!!)

[bitter thicket]

the concept makes sense to u but that's about it. and hence u can't put it into actual code

[dire prawn]

I think school started this week.

[cosmic hemlock]

i watched a ton and you would make a class to not have it al lcrushed in one to make it more understanble

i just didnt get the way ethan did it

[mortal valley]

at its most basic, you can create a list using java class Node { Node next; Object data; }that much makes sense, yeah?

[cosmic hemlock]

well always make em private

thats good

[bitter thicket]

bc ethan tries to step back 10 steps and fill all the gaps in the knowledge u need to know to be really comfortable with ur assignment

[mortal valley]

but you understand how to make a list using a class like that, yeah?

[bitter thicket]

u dont have to follow his path. but then u need someone else to help u out

[cosmic hemlock]

i was praicting making a list with just ints

so i would do it int data

but yea

then i would do a construcotr

then after that make a new class called linkedlist whcih will include all the appends and all of that

[mortal valley]

could you show us, just so we're on the same page?

[cosmic hemlock]

just like this

[mortal valley]

i mean show us how a list would be made using Node objects

thats the class. how would you use that class to make a list?

[cosmic hemlock]

public Node(int data) {
this.data = data;
this.next = null;
}

this will be the construcotr

in that Node class

[mortal valley]

okay, but how would you make the list?

[dire prawn]

This is why I'm an advocate of just giving them answers when they are this green. It hurts no one at this stage.

[cosmic hemlock]

go make a class LinkedList

put methods

i incude head, current, next

i make a new node head

[mortal valley]

with just the Node class

[cosmic hemlock]

referene to the first node in the linked list

[mortal valley]

with only the class i gave you

Node node = new Node(5);```

theres the first node, just to get you started

[cosmic hemlock]

well im starting off with the basics

i understand how to code it

[mortal valley]

this is as basic as it can possibly get

[cosmic hemlock]

then learn how to do it in one class

[mortal valley]

this is the very root of it all

[cosmic hemlock]

i wasnt looking to jumping around

[mortal valley]

if you cant do this, you wont be able to make a linked list

so this is where it starts

linking data

[cosmic hemlock]

theres many ways but i wanted to start off with the basic root

[bitter thicket]

ur not helping the convo and only causing OP to feel bad. please hold urself back and write such comments in another channel, if at all. thank you

[cosmic hemlock]

its okay dont worry

[mortal valley]

this is the root. this is how linked data structures work

[cosmic hemlock]

i dont feel bad im just confused

welps gotta go

food time

thanks for the help guys

[dire prawn]

gatekeeping information because you think "it's for their own good" drives people away.

[cosmic hemlock]

true

[mortal valley]

when you get back, link nodes together

[cosmic hemlock]

okay okay i will

thats the next chapter im reading actually on my book

its old its from 2004

[mortal valley]

this is the first node, you gotta link other nodes

[cosmic hemlock]

i just see vids and try to read

[mortal valley]

its been the same since the beginning of time basically