Invitation to CodeChef October Long Challenge 2019

Greetings CodeChef community!

Did you enjoy our servings in the CodeChef’s September Lunchtime? Hopefully, you achieved an improved rating and a bunch of mouthwatering ACs.

Now, the CodeChef’s October Long Challenge is just around the corner. We urge everyone from our community to take part in this contest, starting 4th October till 14th October. It will be an occasion where you put to test your exceptional programming skills.

The problem statements will be available in English, Hindi, Bengali, Russian, Mandarin and Vietnamese.

Do join your fellow programmers and actively participate in this thrilling contest! Accompanying me on the problem setting panel are:

Contest Details:

Time: 4th October 2019 (1500 hrs) to 14th October 2019 (1500 hrs). (Indian Standard Time — +5:30 GMT) — Check your timezone.

Contest link:

Registration: You just need to have a CodeChef handle to participate. For all those who are interested and do not have a CodeChef handle, are requested to register in order to participate.

Prizes: Top 20 performers in Indian category and top 10 performers in 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:

(For those who have not yet got their previous winning, please send an email to

Good Luck! Hope to see you participating! Happy Programming!


Looking forward to the contest. :grinning:

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Excitated but sessionals are coming.:grin::sweat_smile:

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Let this game begin :fire:


Hope this Challenge won’t be same as September Long Challenge, full of maths. :neutral_face::raised_hands:


However it maybe, we’ll do it this time :heart_eyes:

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Karan be like : swagat kro hamara :crazy_face::rofl::rofl:


Nothing like that. I am just so excited!



I think there’s a problem with the constraints of TANDON, normally a problem accepts a solution which runs in time which is a small multiple of the minimum (expected) time. My solution seems efficient and takes about 2-3 secs in worst case (even with all optimization hacks). Please verify if the time limit is 1 sec or 3 secs.

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Nevermind, I solved it :sweat_smile:


In problem Bacterial Reproduction, I got a different verdict for the exact same solution when resubmitted it. Can anyone explain to me how it happened and can admin look into it as the only test case failed due to TLE in one solution got accepted for the same solution when I resubmitted the same code.
Links to submissions: Submission 1
Submission 2

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JIIT’s time limit is real strict, but most likely because I decided to pursue Cayley instead of going to a combinatorics solution instead.

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Can you please tell your solution idea ? As soon as I saw JIIT, mind went blank…no approach comes to mind even for 10 pts… :slight_smile:

JIIT’s time limit is strict. Had hard time getting last 10 points. My soln was using GFs and NTT was bottle neck for slowdown.

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bhai any try for last one??

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Their notations are making life difficult.
Idk if these are sufficient.

@r_64 expecting introduction about matroids from you in the editorial.
Just saw your blog in chinese. You finished this off in 2 line. I hope thats not the case with editorial.

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I saw the solution which do it in 0.06 sec…

check this


I also had a hard time optimizing the last 10. Firstly I reduced every polynomial into half which helped me get to 90, however after that I have to use polynomial division and a few minor optimizations to the N ^ 2 operations for the full 100.

Also that 0.06s use combinatorics and I did say I probably would have had an easier time if I went in that direction instead :frowning:

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How did you guys approached JIIT, I wasn’t able to think of any optimal solution for it. I haven’t studied many topics so bummer there but it’d be very helpful if someone can share his approach