Check if Array Pairs are Divisible by K | Hashmap Interview Questions Explained

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NADOS also enables doubt support, career opportunities and contests besides free of charge content for learning. In this video, we discuss the problem where we are required to check if the array pairs are divisible by any integer k. In this problem,
1. You are given an array(arr) of integers and a number K.
2. You have to find if the given array can be divided into pairs such that the sum of every pair is divisible by k.
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#hashmaps #datastructures #algorithms
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[@vardhmanjain1630]

In my life, sir , I have never learnt something explained so beautifully. Thanks for all your videos, it really helps .

[@Pepcoding]

Thank you so much and If you like our efforts, please upvote the comments written by the students about Pepcoding here (www.quora.com/What-are-the-good-websites-to-learn-data-structures-and-algorithms )

[@Siddharthnawani]

to handle negative numbers as well, the solution needs to be modified a little. Put the below where-ever you are calculating remainder. int rem = val % k; if(rem

[@maverickreal09]

why not:- int rem=((x%k)+k)%k;

[@AnkitSingh-zj2uc]

didn't work on leetcode

[@LegitGamer2345]

@@maverickreal09 yeah we have to use this instead of rem+=k possibly for overflow reasons since rem+=k gives WA on leetcode

[@abhishekraj7713]

@@maverickreal09 that right...

[@abhishekraj7713]

@@maverickreal09 (a-b) %c ... We can get by modular arithematic property

[@garimakumari4346]

now rewising this playlist again and getting more logic cleaer thanku team pepcoding and summet sir

[@ayushbhardwaj5925]

What a explanation .............sir aapne to Next level samjhaya hai . Fantastic...problem looks so easy after watching your video.

[@Pepcoding]

Thanks and welcome

[@AtulSharma-hy9yo]

very well explained, I like your all explanations, will recommend it to everyone who wants to learn the hashmap questions technique

[@stupidbutcurious6206]

very well explained... i cam across this question while searching for another similar but a littile more complex... can you please help solve.. The Question is:- Given an array of integers of size N, count all possible distinct triplets whose sum is exactly divisible by given integer K. for triplets i, j, k --> i

[@nitunsingh6986]

Sir u must handle negative cases as well. Like what if array elements are negative

[@naikajsevak6090]

I haven't so much deep understanding of math u are great bro

[@jitendrakumawat1000]

Thanks for your great contents. This code will not work for negative integer so I did change to get the remainder let rmd = ((arr[i] % k) + k) % k. Also you can remove the if 2 * rem == k condition because this will be always even if not then either array count will be odd or any other pair will be mismatched. Like arr = 9,39,36 and k = 8 then array count is odd and arr = 9,39,36,54 and k = 8 so 9 and 39 will create one pair and in case of 36 it will match frequency of remainder 4 to itselef 4 but it will not match for remainder 54 % 8 = 6, there is no number exist with 2 remainder.

[@aj9706]

Can u explain this It's suppose to be r1 + r2 = ky Where y>=1 My question is how is r1 + r2 = k ?

[@aj9706]

How are the remainder sum exactly equal to k

[@syeraa9374]

Hey! can you please explain why this formula ((arr[i] % k) + k) % k working for negative numbers.

[@awalkingnosebleed]

I don't think what you are saying correct, I think the check for k/2 is necessary and cannot be omitted.

[@shinobiwolf8133]

Great solution! But sir can provide explanation fro -ve cases.

[@noobhike5609]

Sir is back ❤️❤️

[@yuvrajgarg3847]

SIR PLEASE MAKE A PLAYLIST FOR HASHMAP INTERVIEW QUESTIONS

[@codehustler8582]

Great explaination sir

[@anuragv400]

Great explanation!! :)

[@Pepcoding]

Beta, recursion main itne question ho gye h, ki bacho ki thinking capability bn jaye ki vo naye question ki recursion khud se soch paye, issliye dynamic programming ki series main directly dp solution krvaya gya h. But if you are facing some problem or for clearing your doubts, you can join our community on telegram - t.me/pepcoding

[@sagargupta1615]

Superb explanation.. thanks 😊

[@anssha2643]

Thanks for uploading this. Sir, can you plz upload all the questions related to subarray. I find them very confusing.

[@Pepcoding]

As soon as possible

[@rohansharma4065]

sir please add a test case for k/2, i got correct without implementing that

[@utkarshagarwal587]

This same question came in my google's OA round

[@neerajsaini1748]

Leetcode : 1497 with negative values(we change -ve remainder in positive ) class Solution { public: bool canArrange(vector& arr, int k) { unordered_map m; for(auto x:arr) { int rem=(x)%k; rem=(rem+k)%k; m[rem]++; } for(auto x: arr) { x=(x)%k; x=(x+k)%k; if(x==0) { if(m[0]%2!=0) return false; } else if(k==x*2) { if(m[x]%2!=0) return false; } else { if(m[x] !=m[k-x]) return false; } } return true; } };

[@sushilvarande6223]

No. 1 explaination 👌

[@Pepcoding]

If you like my efforts, I request a review g.page/Pepcoding/review?rc

[@aj9706]

❤️ Beautiful explanation

[@divyanshuchaudhari3257]

Great explanation sir!!

[@abhinavshukla6418]

damn!!u xplained beautifully, i wish i could think like dt

[@milanpatel6240]

Excellent Explanation.

[@AbhiKumar-vt5ns]

Sir Jii you are the best!!!!!!!!!!!!!!!

[@Pepcoding]

Glad to know that you liked the content and thank you for appreciating. The love and respect which I get from you people keep me highly motivated and the same I am able to forward It to you people through my videos. So, keep motivating, keep learning and keep loving Pepcoding😊

[@aj9706]

It's suppose to be r1 + r2 = ky Where y>=1 My question is how is r1 + r2 = k ?

[@ayushbhardwaj5925]

Thanks sir for your time

[@Pepcoding]

Always welcome

[@118_ruchirjain7]

sir leetcode pr yeh code pass nahi ho raha null pointer exception aa raha hai

[@adarshsasidharan254]

Nice explanation but this won't work for negative numbers I think

[@AbhishekMishra-me4mu]

What will be the approach for negative numbers in the array? Nicely explained this one though!!👍👍

[@Pepcoding]

For better insight, visit nados.io, post your doubts, community will help you out there.

[@PritamKumar-mr9wc]

Thankfully got an explanation.

[@Pepcoding]

Glad it was helpful! If you like our efforts, will you like to write a few words about us here (www.quora.com/How-do-I-start-learning-or-strengthen-my-knowledge-of-data-structures-and-algorithms )

[@rohitshinde8478]

Thank you sir very much

[@Pepcoding]

Thankyou beta! I am glad you liked it. I also hope that you are watching till the end and trying to understand the what, how, and especially why of the problem. If you like our efforts, will you like to review us here - g.page/Pepcoding/review?rc

[@ankitgarg2760]

hey @pepcoding team Can you pls provide the optimized solution Explanation of count pairs in array whose product is divisible by k?

[@raipallisiva107]

bro have u got any solution for product divisible by k

[@ankitgarg2760]

@@raipallisiva107 Nope bhai I am looking out for the solution or explanation but no one is able to do so

[@ashwansrivastava6305]

Sir please sort by value and sort by key krke ek video bana dijiye for hashmap..

[@Pepcoding]

ok ji

[@nikeshsingh2081]

Sir, this solution is not valid if remainder is negative or element are in negative.

[@dhruvarora1660]

Also.....If there are Negative numbers in the array....Just put rem + k else of rem in the remainder frequency map.

[@yashtyagi8040]

@Dhruv Arora but why?

[@DEV_Chaudhary_69]

@@yashtyagi8040 itna matt padho beti

[@prashantjain6623]

Nice explanation !!

[@Pepcoding]

Glad it was helpful! and If you like our efforts, please upvote the comments written by the students about Pepcoding here (www.quora.com/What-are-the-good-websites-to-learn-data-structures-and-algorithms )

[@gauravmandal01]

((elements%k)+k)%k anybody who is strugling for negative testcase just change this

[@ajeetworking]

Thank you for the explaination

[@Pepcoding]

You're welcome😊🙏

[@amansamal8233]

op explanation sir

[@Pepcoding]

Thanks. For better experience visit on nados.io, even you can post your doubts on community tab on NADOS

[@nathann4291]

U R AMAZING 👍

[@Pepcoding]

Thank you so much 😀

[@Sunny-cx8ki]

Sir ek baar Manacher's Algorithm padha do pls.....

[@Pepcoding]

hanji jaroor karenge

[@Sunny-cx8ki]

Thank You very much Sir

[@codestreak6638]

The explanation is too good it will be best if agar c++ code bhi hota 😅😅

[@Pepcoding]

Nados.io pe cpp Mei bhi hai

[@codestreak6638]

@@Pepcoding Got it now I can say best it is😎😎

[@rohankumar-of5qe]

Sir could you help me solve the below problem 🙏🙏🙏 You are given an array of 2N positive integers. There are N rounds in total. In each round you have to choose any two positive integers from the array and delete them. Your score in each round will be gcd(num1 , num2) * round_num where num1 & num2 are the numbers you have chosen. And round_number is the current round. Your total score will be the summation of the scores that you have obtained in every round. Determine the maximum total score The round number starts from 1 Ex-- N = 3 A = [8 5 6 25 6 16] O/p : 41

[@harshtekriwal131]

Sir explanation mast hai, par jo leetcode pr question hai usme negative number bi hai, to uske lie ye satisfy ni hoga. Ek bar wo wala case kese cover krenge wo bi batado.

[@ankoor]

Use ((x % k) + k) % k to calculate remainder, everything else is same

[@Pepcoding]

Ji, mujhse case choota hai. Jo neeche comment mei trick btaya hai wo correct hai

[@harshtekriwal131]

@@Pepcoding Sir ap is trick ka kisi video mei explanation dedijiega

[@maverickreal09]

@@ankoor why not :- int rem=x%k; if(rem

[@ankoor]

@@maverickreal09 this also works too...only difference is I am taking mod again...it doesn't matter...

[@bartosz3667]

If we don't include that 2*rem=k case in our code then also our code will run successfully and efficiently.

[@awalkingnosebleed]

I dont understand how??

[@jyotidhatarwal9753]

Sir if the constraints were -10^9

[@Pepcoding]

Beta, I regret to inform you that, I won't be able to answer/solve the personal doubts of each and every student over here. For clearing your doubts, you can join our community on telegram - t.me/pepcoding.

[@sachinpandey4095]

In this case you can add k to the remainder if the remainder is negative (for negative numbers).

[@targetsubconscious3003]

if (r

[@utsavgupta746]

@@sachinpandey4095 bhai iska logic bata do kyu add kiya?

[@tanishkumar6682]

understood

[@umangkumar2005]

when k=odd then in this k/2 case will fail

[@rahulranjan7567]

There's a hack for this question. If the length of the array is odd, return False else search for the solution

[@rmeena840]

What about negeative numbers?

[@Pepcoding]

Hey there! For better experience and well organised content visit - nados.pepcoding.com You can also post your queries on community tab and follow us on Instagram we will keep you updated. instagram.com/pepcoding/

[@shivanigupta_19]

😍

[@anchalpandey2787]

Greate explanation !!!

[@Pepcoding]

Thankyou beta! I am glad you liked it. I also hope that you are watching till end and trying to understand the what, how and especially why of the problem. Will you like to write a few words about us here ( www.quora.com/What-are-the-good-websites-to-learn-data-structures-and-algorithms )

[@anchalpandey2787]

@@Pepcoding yeah sure

[@jitenderyadav721]

Sir pehle graphs ka dalna tha na

[@Pepcoding]

wo bhi aaega beta jaldi he

[@RITIKYADAVBIT]

leetcode 1497 solution class Solution { public boolean canArrange(int[] arr, int k) { Map rf = new HashMap(); for(int val:arr){ int rem = val%k; if(rem

[@maverickreal09]

how to handle negatives?

[@Pepcoding]

Beta, I regret to inform you that, I won't be able to answer/solve the personal doubts of each and every student over here. For clearing your doubts, you can join our community on telegram - t.me/pepcoding.

[@maverickreal09]

@@Pepcoding Ok sir, n.p. Thanks for the reply.

[@W0807THORE]

Can we add all the elements and module division by k and if module result is O and array length is even then we can print true else print false?? Will it work here

[@Pepcoding]

1, 2, 3, 1, 2, 3 and k is 6 this strategy won't work

[@user-fz1cj8rh6k]

Make videos in English.