i <= newArr.length+start-1 . I abit confused with this formula. | Java Community | Help. Code. Learn. | Page 1

deep zephyr May 10, 2023, 6:47 PM

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import java.util.Arrays;

public class Main{
    public static void main(String[] args) {
        System.out.println(Arrays.toString(fizzBuzz(2, 8)));

    } 
    public static String[] fizzBuzz(int start, int end) {
        String[] newArr = new String[end-start];
        for (int i = start; i <= newArr.length+start-1; i++) {
            if (i%3==0 && i%5==0) {
                newArr[i - start] = "FizzBuzz";
            } else if(i%3==0){
                newArr[i - start ] = "Fizz";
            }else if (i%5==0){
                newArr[i - start] = "Buzz";
            } else {
                newArr[i - start] = Integer.toString(i);
            }
        }
        return newArr;
 }
}

pearl creekBOT May 10, 2023, 6:47 PM

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deep zephyr May 10, 2023, 6:47 PM

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if i = start it means that both i and start are 2 in this case

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the length of the arr is 8 - 2 which is 6 but why do we add 2 to 6 and then subtract 1?

hoary rock May 10, 2023, 6:49 PM

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you kinda don't, that's kinda poorly written

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it should be more like i < newArr.length + start, or just i < end

deep zephyr May 10, 2023, 6:51 PM

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yeah chatGPT wrote it and confused the hell out of me hahah

plush pilot May 10, 2023, 6:51 PM

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but still, array indexing of newly created array starts from 0, it's not iterating through existing array with provided start and end

hoary rock May 10, 2023, 6:51 PM

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newArr.length = end - start, end = newArr.length + start
i < end is equivalent to i <= end - 1 (because i is an integer)
thus, i < end is equivalent to i <= newArr.length + start - 1

hoary rock May 10, 2023, 6:51 PM

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deep zephyr yeah chatGPT wrote it and confused the hell out of me hahah

and this is why you don't use chatgpt

deep zephyr May 10, 2023, 6:52 PM

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tbh my math is reaaaly bad

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that is why I struggle to understand these basics

hoary rock May 10, 2023, 6:52 PM

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chatgpt certainly isn't going to help it

deep zephyr May 10, 2023, 6:52 PM

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well so far it has been quite helpful haha but yeah I agree

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the thing is I am confused about which i is index and which i is start

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or if i = start it will always be start?

hoary rock May 10, 2023, 6:54 PM

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deep zephyr the thing is I am confused about which i is index and which i is start

neither

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i = start is only the initial value

deep zephyr May 10, 2023, 6:54 PM

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so i = start which is 2 in our case will i++ so in the next iteration it will be 3 then 4 and so on?

hoary rock May 10, 2023, 6:54 PM

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yes

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i is used to derive the index, but it isn't used as the index directly, there's an offset of start

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do you know how a typical array loop would look like

deep zephyr May 10, 2023, 6:55 PM

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I am used to i = 0 but sometimes i needs to be initiated to something else

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yeah

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I even solved reverse array problem myself haha

pearl creekBOT May 10, 2023, 6:56 PM

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deep zephyr I even solved reverse array problem myself haha

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deep zephyr May 10, 2023, 6:56 PM

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which I am very proud about

hoary rock May 10, 2023, 6:56 PM

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deep zephyr I am used to i = 0 but sometimes i needs to be initiated to something else

yeah

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notice how, compared to a normal loop, the start and end have start added, and inside the loop, i has start subtracted

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that normalizes the value to get a proper index

deep zephyr May 10, 2023, 6:57 PM

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wait a moment I will try to understand i < end

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ok so if start is 2 and end is 8

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then i = 2; i < 8 which excludes 8 and makes it 7

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but we only have 6 numbers coz 8 - 2 is 6

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where will the remaining one go?

hoary rock May 10, 2023, 6:59 PM

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nowhere

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there's 7 numbers

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there's 6 non-zero numbers

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subtraction excludes both ends, but ranges in programming include the start

deep zephyr May 10, 2023, 7:00 PM

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I think for the sake of simplicity let's do 1,5

hoary rock May 10, 2023, 7:00 PM

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wait no, misread

deep zephyr May 10, 2023, 7:00 PM

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start = 1, end = 5

hoary rock May 10, 2023, 7:00 PM

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give me a sec

deep zephyr May 10, 2023, 7:01 PM

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the first element of newArr is at index 0

deep zephyr May 10, 2023, 7:01 PM

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hoary rock give me a sec

sure

hoary rock May 10, 2023, 7:01 PM

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which excludes 8 and makes it 7
you're thinking of i = 1 as a start here

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suppose a higher start, i = 5; i < 10

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this has 5 numbers, 5, 6, 7, 8, 9

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equal to 10-5

deep zephyr May 10, 2023, 7:02 PM

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ok so start is 5 and end is 10 right?

hoary rock May 10, 2023, 7:02 PM

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yeah

deep zephyr May 10, 2023, 7:03 PM

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yes

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i < end at first iteration it is 5 < 10

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then 6<10, 7 8 9< 10

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and 10 is excluded of course

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i - start is 5 - 5 then 6 - 5 so we get 0 and 1 indexes and put 5 at index 0 and 6 at index 1 and so on until 9

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right?

hoary rock May 10, 2023, 7:08 PM

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yeah

deep zephyr May 10, 2023, 7:08 PM

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omg it is so simple jesus

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like who would come up with a monstrosity like newArr.length+start-1

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tbh I still do not get what this is newArr.length+start-1

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ok so basically

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if we need something from start to end like in this example and not including the end we make i<end and if we wanna include the end we make either i<end+1 or i<=end correct?

hoary rock May 10, 2023, 7:12 PM

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deep zephyr like who would come up with a monstrosity like newArr.length+start-1

noone.

hoary rock May 10, 2023, 7:12 PM

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deep zephyr if we need something from start to end like in this example and not including th...

usually i <= end for explicitness, but yeah i < end + 1 would also work

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choose between < and <= for start/end number inclusion
choose between n and n - 1 for element inclusion

deep zephyr May 10, 2023, 7:13 PM

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yes I would use this one as well i <= end

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thank you so much

pearl creekBOT May 10, 2023, 7:14 PM

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deep zephyr thank you so much

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deep zephyr May 10, 2023, 7:14 PM

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Do you know objects and classes?

hoary rock May 10, 2023, 7:14 PM

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i mean, i kinda have to..

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kinda the entire soul of java

deep zephyr May 10, 2023, 7:15 PM

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haha well I am a beginner as you can see

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so still struggling with some puzzles/concepts

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the problem with classes section in my course is the naming convention

hoary rock May 10, 2023, 7:15 PM

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yeah, that's understandable for a beginner

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the first language is always the hardest

hoary rock May 10, 2023, 7:15 PM

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deep zephyr the problem with classes section in my course is the naming convention

what about it?

deep zephyr May 10, 2023, 7:16 PM

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Person person = new Person(people[person]) person person perspon blah blah hahaa

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I used to learn Python last fall

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but then I had to stop for 3 months and now I am back but this time I decided to switch to Java

hoary rock May 10, 2023, 7:16 PM

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oh god...

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did you learn about classes in python

deep zephyr May 10, 2023, 7:17 PM

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just a tiny little bit so I would say no

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why?

hoary rock May 10, 2023, 7:17 PM

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python classes are implemented in a way that... idk how to describe it. painful, i guess

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it's a bastard of OOP lmao

deep zephyr May 10, 2023, 7:18 PM

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tbh I noticed that I understand for loop better in Java than in python

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and all those indentations in Python geez

hoary rock May 10, 2023, 7:18 PM

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welp, good that you haven't gotten to classes in python yet

hoary rock May 10, 2023, 7:18 PM

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deep zephyr and all those indentations in Python geez

they enforce good formatting, they aren't all bad

deep zephyr May 10, 2023, 7:19 PM

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yeah but being afraid of tabs vs spaces

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is kinda scary haha

hoary rock May 10, 2023, 7:19 PM

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it isn't though

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using a single style is proper formatting

deep zephyr May 10, 2023, 7:20 PM

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so here is a piece of code from my class

    public Person getPerson(int index){
        Person person = people[index];
        return new Person(person);
    }

    public void setPerson(Person person){
        int index = person.getSeatNumber()-1;
        people[index] = new Person(person);
    }```

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like the naming is just frustrating

hoary rock May 10, 2023, 7:20 PM

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person/people is probably a bad example to get started on tbh

deep zephyr May 10, 2023, 7:21 PM

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and trying to decipher which is which and like the topic of arrays with objects inside is painful now for me

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we had cars first

hoary rock May 10, 2023, 7:21 PM

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plural variable names (when there's a singular counterpart) generally refers to a structure holding the singular form of that name

deep zephyr May 10, 2023, 7:22 PM

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like it's been a week or more since I started OOP and I thought I would understand it all and move on to the next topic but here I am rewatching stuff everyday trying to understand what is going on

deep zephyr May 10, 2023, 7:22 PM

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hoary rock plural variable names (when there's a singular counterpart) generally refers to ...

yeah this one I get / Car[] cars and Car()

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how long did it take you to understand objects, constructor, deep copying , getter and setter? if you remember of course

hoary rock May 10, 2023, 7:25 PM

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for java, probably within a few minutes; but that wasn't my first time learning the concepts
i learned them over weeks from js, wasn't really following any real course then

i have those answers but they aren't really useful to you, eh

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why ask about other peoples' experiences though? they don't matter to you, or at least, they shouldn't; everyone learns at their own pace, everyone has a different background, different ways to learn, different ways to handle new information

deep zephyr May 10, 2023, 7:26 PM

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yeah I am happy that concepts are more or less the same which means I can learn another language once I am super confident in Java

deep zephyr May 10, 2023, 7:26 PM

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hoary rock why ask about other peoples' experiences though? they don't matter to you, or at...

100% agreed

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but you know it is really hard emotionally so I guess I seek comfort

hoary rock May 10, 2023, 7:27 PM

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fair enough

deep zephyr May 10, 2023, 7:27 PM

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for example this.everyone learns at their own pace, everyone has a different background, different ways to learn, different ways to handle new information

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I feel better when I read something like this 🙂

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there is a lot of discouragement in the IT industry such as "you have to be good at math/ you have to be passionate about programming, you have to be this and that"

hoary rock May 10, 2023, 7:28 PM

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there is a barrier to entry, but it's not that drastic tbh

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computer and internet literacy are must haves, but math knowledge isn't really required, it just makes it a lot easier; if you didn't know it before (and you actually care about learning) then you'll just spend some time learning that same math knowledge under the guise of programming instead

deep zephyr May 10, 2023, 7:29 PM

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Do you work with Java? if yes how long have you been working as a developer? idk about the names of the profession yet

hoary rock May 10, 2023, 7:30 PM

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i don't do programming professionally, no

deep zephyr May 10, 2023, 7:30 PM

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hoary rock computer and internet literacy are must haves, but math knowledge isn't really r...

yes that is what I am doing now. Like in school hehe

deep zephyr May 10, 2023, 7:30 PM

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hoary rock i don't do programming professionally, no

oh ok

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programming has always been the last thing I was interested in and so was math and things like that, I think that is why my logical skills kinda suck

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But life has its own ways you know

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And now I am here and learning the things I was intimidated by all my life and thought I could never do it

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And with each day I begin to believe that actually I can do anything

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You just gotta want and work towards stuff you know

hoary rock May 10, 2023, 7:33 PM

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that's a great mindset to have

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wish more people had that kind of mindset...

deep zephyr May 10, 2023, 7:33 PM

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I am trying

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I have a friend who is a senior java dev

hoary rock May 10, 2023, 7:33 PM

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you really don't

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oh god i misread that lmao

deep zephyr May 10, 2023, 7:34 PM

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what? haha

hoary rock May 10, 2023, 7:34 PM

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i read that as "i need a friend [...]" lmao, quite a people say that to mean they want help

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god i should go to sleep soon, it's 2:30am here lol

deep zephyr May 10, 2023, 7:35 PM

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oh so yeah I asked him about help and he said once I get to a certain level he can give me real projects and then help me understand/solve them

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it is 22:35 here

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My brain is kinda not working too haha

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it's been nice talking to you

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thank you for your help and wisdom 🙂

pearl creekBOT May 10, 2023, 7:36 PM

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deep zephyr thank you for your help and wisdom 🙂

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deep zephyr May 10, 2023, 7:36 PM

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Good night 😴

#i <= newArr.length+start-1 . I abit confused with this formula.