Subarray Sums Divisible by K - Leetcode 974 - Python

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Problem Link: leetcode.com/problems/subarra...
0:00 - Read the problem
0:30 - Drawing Explanation
14:30 - Coding Explanation
leetcode 974
#neetcode #leetcode #python

[@shazam3218x]

I have a two technical interviews on Wednesday and Thursday. Hopefully I clear them and get the job🤞 Edit - Dint get selected for next round. I'll keep leetcoding until I get another job

[@AdityaRaj-xm6oi]

Good luck buddy

[@chrischika7026]

goodluck, and comeback to this comment to tell us how you did.

[@NeetCodeIO]

Good luck you got this!!!

[@akakop]

Hopefully I get this question

[@varunagarwal1756]

You guys are getting interviews?

[@akash-kumar737]

Pattern is same as yesterday problem. Thanks man your explanation helped me solve this on my own.

[@yang5843]

Thanks for uploading this, the issue I realized I was having with this problem was due to negative numbers being modded in Java

[@chaitanyasharma6270]

-1%5 is 4 in python but in other languages, java c#, javascript it is equal to -1. curr+=nums[i]; int key = curr % k; if(curr

[@YashTech16]

if sum is -5 and k = 5 then key is 0 but as curr < 0 key would be changed Hence one more condition required curr += nums[i]; int key = curr % k; if(curr < 0 && key != 0){ key += k; }

[@ameydhimte_c5956]

@@YashTech16 key won't be zero buddy. How would you make a sum divisible by 0

[@Antinormanisto]

I understand how it's 4 Just some math that i hate: a = -1 // 5, how to do it? -1 / 5 = -0.2, round it to the floor. a = -1. -1 % 5(it's b, ok?) = -1(a) * 5(b) + x -1 % 5 = -5 + x. x is 4 because we need to find the x that will give the first number(-1) after plusing the x with the result -1(a) * 5(b) (-5) -1 = -5 + x 4 = x Sorry if I made a mistake, but I heard this solution how to solve mod(%) with negative numbers

[@markuscwatson]

This works in typescript: `let rem = ((sum % k) + k) % k;`

[@marcoaraujo9446]

But with regard to this difference, do you know why? Why does python have a different result to java, shouldn't the operation be implemented in the same and be agnostic from programming language ?

[@maanas_sehgal]

Hey @Neetcode Can you please upload solutions for contests as well. It would be really helpful😊

[@MP-ny3ep]

Great explanation as always. Thank you

[@thomasmcnutt252]

much easier to understand than the leetcode editorial! Nice job!

[@rumonintokyo]

That is a great explanation thanks a lot but coming up with it during an interview is another challenge altogether!!

[@fiascogamingchannel78]

pretty much got this thanks to yesterdays leetcode daily problem and by figuring out the pattern of how the occurence of multiple remainders are contributing in final ans

[@EliasKibret]

Main Point : If two prefix sums have the same remainder when divided by 𝐾 ,the subarray between these two prefix sums is divisible by 𝐾

[@fancypants6062]

this channel is so good

[@AJK-a2j00k4]

Crazy intuition fr!

[@jensenzhang2452]

thank you neetcode!

[@sidreddy7030]

Yayyy you’re finally back

[@chien-yuyeh9386]

Nice!!😊

[@nnkbrain]

Hey can you also solve the contest questions ❓

[@saisurisetti6278]

Ok I’m too addicted to these videos.. I need to stop.. this is past my bed time lolz

[@user-he4st2ro5h]

I didn't get it. In this particular case divisible doesn't mean evenly divisible, i.e. it doesn't have to be prefix_sum % k == 0?

[@pastori2672]

woudlt an array actually have n! subarrays since your starting at every position and each time decrementing one so it would be like n * (n - 1) * (n - 2)... ?

[@user-ns7tu5no1i]

i always stuck on these kind of problems why i dont get a intution of solving them , I mean optimize solutions.

[@s8x.]

bro what’s ur routine like

[@nirmalgurjar8181]

For java programmers if remainder is -ve then just add k to it to make it positive same as python does and all will be right. if(rem < 0) rem = k + rem;

[@zinnia993]

Can you explain why (remainder < 0) remainder = k+remainder works?

[@zweitekonto9654]

Read about modular arithmetic for negative numbers.

[@DeathSugar]

For whoever stuck on "wrong" remainders for negative numbers - use Euclidean remainder instead of default % operator. It goes like (n % m + m) % m.

[@gagandhand8907]

For negative remainder, its not working.

[@tai-xinyu407]

Because of the problem yesterday, 523, I watched the video of 560, but I still feel a little confused about 523. Will you explain and upload it? Even make it into shorts would be helpful.

[@Stopkaaaa]

He already did it kzbin.info/www/bejne/hXzGo3-ch5Jro6c

[@gagandhand8907]

Will it work for negative remainder? For me its nor working.

[@its_shivam_jha]

yaa it doesn't work for me too

[@abid3801]

Bro, Your teaching is nice. It would be nicer if you took care of your accent. Please do

[@venusshili]

why we don't need check the remainder is positive?

[@hesheid9159]

python take right remainder we dont need to check it

[@yxchen6080]

@@hesheid9159 does it mean that the logic of this solution is only for python? In other language, we need to adjust the remainder to positive by ourself?

[@zinnia993]

@@yxchen6080 yes we need another check if remainder is negative

[@RACM27MD]

Hint: If you're not using python, don't forget to adjust the remainder to be a positive number in case the language you're using returns a negative remainder. if (remainder < 0) remainder += k;

[@aviksain]

This is in python that's way we don't have to do this int remain = (prefix_sum % k + k) % k;

[@iluvDDOI]

Thanks man. btw why did it not work in c++ as it works fine in python

[@aviksain]

@@iluvDDOI Because in python compiler if you modulo some number it gives a positive number like this -4%7 = 3 but in c++ we will get this -4%7 = -4 thats way we have to convert the negative numbers into positive number for the question to match the previous reminder and count it.

[@user-qp5cw8sd4w]

first

[@vishruthpuli1664]

Third

[@stormShadow64]

I still don't understand it

[@MehmetDemir-xi3yy]

Bob ross reference

[@upsidedownChad]

Forth

[@nikhil199029]

Am I stupid or this problem was hard? prolly I am stupid 😅

[@sabukuna]

its a big math gap. i couldnt do it either.

[@Antinormanisto]

I'm like a monkey being taught P.s I didn't understand an explanation