Invitation to CodeChef October Cook-Off 2020


I am thrilled to invite you to participate in CodeChef’s October Cook-Off, this Sunday, 18th October, from 9:30 pm to 12:00 am IST.

Followings are the basic information:

  • Participants in each division will be given 6 problems and 2.5 hours to solve them.
  • All problems have been cooked by me.
  • Statements are very short unlike this announcement!
  • Problems will have strong samples.
  • There will be an interactive problem in this round, so, you should know how to deal with them.
  • I hope your internet connection is good as some of the problems will feature awesome animations that I have created using Manim! Yeah, it means the problems will have better explanations.
  • In my last contest, only 103 div2 participants managed to solve div2C which is not good at all. So this time I have tried to maintain a more balanced difficulty distribution.
  • I would like to thank teja349 for his brilliant coordination of this round.
  • rahuldugar tasted the problems(I hope they taste sweet!). I want to thank him particularly for helping me with the preparation of a few problems.
  • psychik is in charge of the editorials.
  • Needless to say, xellos0 did the statement improvements.
  • Video Editorialists: chirayu_98, prachi16121996,darshancool25, kiritsuguemia, divesh2201
  • Translators: gomelfk [Russian], Team VNOI [Vietnamese], solaimanope [Bengali], devils_code [Hindi], sam__2 [Mandarin]

Regarding the collision between Codeforces div2 and this contest: Even if you don’t participate in this contest, I would still encourage you to check out the problems after the contest.

Prizes: The top 10 Indian and top 10 Global participants will receive CodeChef laddus, with which the winners can claim cool CodeChef goodies. Know more here.

The video editorials of the problems will be available on our YouTube channel as soon as the contest ends. Subscribe to get notifications about our new editorials.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef’s contests, you can share them here.

Good luck!


The video editorials to the problems are uploaded on Youtube

logic for Yet another Crossover Episode?

if the value of D <= 10**5, it would be a piece of cake !! XD

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The final array will be a combination of 2323…1…323232…1…2323 etc

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I hate it when I have a solution that is wrong but I don’t know why its wrong. Spent an hour trying to find cases that don’t work on my code for XOXO and found nothing

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can you please give little more brief about your logic, I did not get it

Appreciate those cool animations!

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Array of type 23232 with length k will give a value of k*(k-1)/2 . So I basically find the the largest k such that k*(k-1)/2 <= n and append a pattern of length k to it, decrease k and go on. I add 1 in between as it’ll seperate and I can take sum of seperated patterns

Ex: For 16: first i add pattern of length 5 to get 23232 and total pairs is 10. Then i append a 1. Now the remainder is 6 so i add pattern of length 4 which gives 2323212323 and total is 16


Lol. Yea. But i found the pattern for even bigger numbers. xD