Invitation to CodeChef December Long Challenge 2020

We invite you to participate in CodeChef’s December Long Challenge, this Friday, 4th December, from 15:00 IST onwards.

The contest will be open for 10 days i.e. until 14th December.

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.

Joining me on the problem setting panel are:

anton_trygub Trygub, Md. Reyad fiction1729 Hossain

darshancool25 Lokhande, Yashodhan Agnihotri (, Bharat Singla (, Aryan Agarwala (, Radoslav Dimitrov (

  • Statement Verifier: Jakub xellos0 Safin

  • Mandarin Translator: Hanlin r_64 Ren

  • Vietnamese Translator: Team songuku95 VNOI

  • Russian Translator: Fedor gomelfk Korobeinikov

  • Bengali Translator: Mohammad solaimanope Solaiman

  • Hindi Translator: Akash devils_code Srivastava


Top 20 performers in the Indian category and top 10 performers in the Global category will get CodeChef laddus, with which the winners can claim cool CodeChef goodies. First to solve each problem except challenge - 100 laddus. 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.

Good Luck!

Hope to see you participating!!

Happy Programming !!


Sorry to say this , but if 300iq/ildar_adm is a problem-setter of a contest on Codechef, then there is a high probability of the contest being un-balanced .

So , all the long challenge guys, get ready for the fun. lol(I never gave long challenges though xd)

Its my polite request to you, that in the next contest(lunchtimes and cookoffs , please make problems which are balanced and don’t put 4 problems in Div-1 short contest which can only be solved by 7* in that contest . Please maintain the Codechef traditions of good algorithmic balanced problems in short contests. I hope you will take the constructive feedback.


I hope there is no problem whose algorithm is well-known only in Russia/China.


Why is there no challenge/tiebreak question this time?

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Maybe they’ll add it later.

It is more like a Maths Olympiad :frowning:

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Hi all, Does every problem in the long challenge carry equal weight age or is it proportional to the difficulty?

Equal weight-age

Video editorials for 9 problems have been uploaded on Youtube. The other 3 videos will be uploaded over the next day or two. And the written editorials can be found here. Remaining 2 editorials will be added soon.

Why the DIGMATRIX video solution is not present , as well as Editorial.

And my guess was right, integration question was a big disappointment for many.

This is my first long challenge solved the first four question. Very sad to see lot of people cheating. Had no idea how to solve HailXOR, tried hard to solve STROPERS, but even my brute force solution didnot get accepted. Gave up, but at 23 hours left tried to take a stab at LCASQRT, initially thinking there is no way I can solve it. But pushed through and managed to solve atleast the first test case in LCASQRT with the others as TLE, which is a silver-lining. I am partly satisfied at that. Long way to go for me!


When can we expect the editorial for DGMATRIX, it’s been 5 days, and still, there is no video editorial or editorial. :frowning: