harshith_04's blog

By harshith_04, 5 weeks ago, In English

We invite you to participate in CodeChef’s Starters 173, this Wednesday, 12th February, rated for users with rating < 2700.

Joining us on the problem-setting panel are:

Written editorials will be available for all on discuss.codechef.com. Pro users can find the editorials directly on the problem pages after the contest. The video editorials of the problems will be available only to Pro users.

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. Hope to see you participating.

Good Luck!


CodeFest is a premier competitive programming event brought to you by IICPC, powered by Hudson River Trading (HRT), co-sponsored by Citadel Securities and Jump Trading with Jane Street, The D.E. Shaw Group and Landeed as Associate sponsors and QuantInsti being the Knowledge Partner.

Codefest is a 3 stage Individual Contest:

  • Stage 1 (Prelims) : To be held on Codechef on 12th February 8pm IST
  • Stage 2 (Offline Regionals) : 2 Multisite Regionals to be held across 8 IITs.
  • Stage 3 (Grand Finale) : To be held in Research Par[user:NAchia]k IIT Madras on 5th April while 6th April 2025 is booked for recruitment round for the firms interested in students through an interview process.

Qualification

There are 400 slots in the Regionals and 50 for the Finals.

  • (Prelims to Regionals Qualification) : In the CodeChef Contest, all divisions will have a common Problem set. Top 400 over the aggregate ranklist will move on to the Offline Regionals.
  • (Regionals to Finale Qualification) : Top 25 participants from each of the 2 regionals will move on to the Grand Finale.

Prizes

  • Certificates for the Top 2,000 rankers in Prelims.
  • For Indian Participants: Prize Pool of ~ ₹10,00,000 and work opportunities at our sponsors — Elite International HFT firms (High school, UG, Dual Degree students are all eligible).
  • For International Participants: Prize Pool of ₹25,000 to the Top 5 participants in the Prelims leaderboard.

Register now at iicpc.com (plesse clear cache if old website is popping up; new website contains information for Codefest 2025)

More information can be found here — [Invitation] IICPC CodeFest 2025


Congratulations to the Winners

  1. Nachia
  2. Rubikun
  3. snuke
  4. potato167
  5. shiomusubi496

Thanks for participating; results of Prelims can be found on https://iicpc.com/prelimsresults

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5 weeks ago, # |
  Vote: I like it +18 Vote: I do not like it

As a setter, I hope you like the contest.

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Rev. 2   Vote: I like it +3 Vote: I do not like it

Waiting

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5 weeks ago, # |
  Vote: I like it +18 Vote: I do not like it

As a tester, shrek wishes you good luck.

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5 weeks ago, # |
  Vote: I like it +9 Vote: I do not like it

hoping to see a good set of problems

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5 weeks ago, # |
  Vote: I like it +5 Vote: I do not like it

Excited for contest

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5 weeks ago, # |
  Vote: I like it -22 Vote: I do not like it

This contest will only take me 5 minutes to complete

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5 weeks ago, # |
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Excited ✨✨

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5 weeks ago, # |
  Vote: I like it +5 Vote: I do not like it

Prize pool is only for students? Not for working ones?

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4 weeks ago, # |
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Can we fill regional centers choice after Prelims?

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    4 weeks ago, # ^ |
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    You'll be given the choice to edit your regional centre preferences after the Prelims if you are in top 400.

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4 weeks ago, # |
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Slots of 400 is for 8 iits total or one iit 400 slots

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    4 weeks ago, # ^ |
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    Top 400 in prelims, will be assigned to 8 IITs — ~ 50 per regional centre

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4 weeks ago, # |
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₹10,00,000

Wtf is this number?

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4 weeks ago, # |
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Is registration at https://iicpc.com only meant for students? I see a mandatory Graduation Year field which only provides options from 2025 to 2029 and another School option for under-university schooling students.

I will be able to participate directly on CodeChef Starters 173, but I didn't see any eligibility criteria mentioned for registration. I see a comment that only students are eligible for prizes. Please confirm on who should go for registration as well.

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    4 weeks ago, # ^ |
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    Everyone are welcome to participate, for students it's CodeChef starters + Codefest prelims; for others it's a usual starters round.

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4 weeks ago, # |
  Vote: I like it +17 Vote: I do not like it

As a first-time tester, I hope you enjoy the problem set :)

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4 weeks ago, # |
  Vote: I like it +8 Vote: I do not like it

As a setter (love that I can say this!), I hope you enjoy the problems :D

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4 weeks ago, # |
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How are you going to make a combined rank list when div4 are supposed to do 3-4 extra problems than div1

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    4 weeks ago, # ^ |
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    "all divisions will have a common Problem set" similar to CF Div1+2

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      4 weeks ago, # ^ |
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      so will the standings for all the divisions will be same during the contest or we will have to wait for official standings after the contest to know if we qualified or not

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        4 weeks ago, # ^ |
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        Ranklist will be separate per each division, you can get a combined one only after the contest ends.

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4 weeks ago, # |
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As a organisor, I hope you have fun :)

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4 weeks ago, # |
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Highlight the part of ranking system that this time it is icpc which is unusual, otherwise people will say again I didn't see that

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Reminder: Contest starts in ~45 minutes — https://www.codechef.com/START173

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4 weeks ago, # |
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Contest starts in ~30min.

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4 weeks ago, # |
  Vote: I like it +28 Vote: I do not like it

It was a good idea to add the first problem as Time Penalty to make sure everyone knows there is a penalty for incorrect submissions. Appreciate the effort from authors.

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4 weeks ago, # |
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where to see the leaderboard of all divisions ?

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4 weeks ago, # |
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I got WA on test 12 in problem INTROVERTS

my idea was to achieve the main goal

My Code

I think the problem is that I didn't handle the case where I have to achieve the secondary goal, am I right ?, or there is something wrong with my approach to achieve the main goal ?

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    4 weeks ago, # ^ |
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    2nd goal only needs to be considered for the first slot. The rest of them are fixed.

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      4 weeks ago, # ^ |
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      Can you explain a bit more on this 2nd goal?

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        4 weeks ago, # ^ |
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        You only need to consider the 2nd goal for the 1st person. It results in the condition that 1 must lie on the end of the array. After that, the maximum closest distance for the entering person will always be fixed (There may be multiple such positions where the person may sit).

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          4 weeks ago, # ^ |
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          Solved. I was taking minimum distance instead of maximum distance. I forgot to use greater<> in my set. Anyone did it without max set + min/max Segment tree can share any simpler approach? My Approach

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        4 weeks ago, # ^ |
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        I assume you understand how to pick the first seat. It should be either seat 1 or seat N. Let's say 1st person take seat 1, then the 2nd person has no choice to pick seat N to achieve goal 1. The 3rd person has to take seat in the middle to achieve goal 1. If odd number of seats left, 3rd person has no choice but taking the middle one, If even, there are 2 choices but both of them satisfying goal 2 so he can take either of them. It's not hard to see it will be the same process for the rest of people and once goal 1 is achieved goal 2 is also achieved.

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4 weeks ago, # |
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No Idea why my 2^n recursive solution for Cool checker Passes .. I just generated all the subsequences and stopped when i found a average not in B array .. But I thought It would give TLE when we have a big array with all same elements but surprisingly it passed .. I earlier was trying to do it with only distinct elements but it was giving WA (hence tried with all elements later)..

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    4 weeks ago, # ^ |
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    No matter what array you take in 1 of the possible subsequence, there will be always be a single element existing and for that in the complement there has to be the same element that is every element in the array must have a duplicate so just find any element that is repeating more than once. DONE.

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      4 weeks ago, # ^ |
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      actually i was not concerned about the solution of the problem , rather i was thinking how my code works .. If u simply give me an array of 1e5 size with all same elements and array b containing that element My code should surely give a TLE .. But it works somehow .. Are the testcases that weak ?my accepted submission

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      4 weeks ago, # ^ |
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      i think u are talking about the cool subsequences problem .. I was talking about cool checker problem

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        4 weeks ago, # ^ |
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        My Bad. Up-solving this now.

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        2 weeks ago, # ^ |
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        Necropost.

        Hey man I finally solved this. I can answer your question now but you probably already have figured it out with the editorial. Just wanted to close this verbal contract.

        If the length of the array is actually large and all elements are equal, your code should TLE and test-cases are weak. You can check this for this input. It took around 12 seconds average over 10 calls and MLE so have to increase the stack size.

        Test case

        In the following contest also they had weak test cases which lead me to pass a question with very weak intuition and guesswork here.

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          2 weeks ago, # ^ |
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          But I don't think the testcases were weak , because the next day when I submitted same solution it was giving TLE .. Also the testcase to make it fail is pretty simple and obvious so I think there must be something wrong with compiler or judging from cc end .

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            2 weeks ago, # ^ |
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            I still believe its weak test cases. Maybe some optimization like pre-tests or something during live contests or lazy test cases added post contest after examining buggy solutions. This is actually testable as to why it happened but I have to wait till the next round. I'll update you on Wednesday.

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              2 weeks ago, # ^ |
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              how would u test it ? like what will u do in contest ..

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4 weeks ago, # |
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Hi, this it to inform that the Codechef compiler was judging INCORRECTLY during starters 173.

Kindly look into it as it ruins the contest experience. harshith_04

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    4 weeks ago, # ^ |
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    It's because your code's run time is very close to the TL of the problem. Nothing can be done here.

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4 weeks ago, # |
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Do we need to have the same email id linked with the codechef account as the one used for registration?

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    4 weeks ago, # ^ |
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    It is not required; the email is just a point of contact. We'll be verifying cc accounts of the top 400 after removing cheaters.

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Please use this form to report any suspicious codes you come across in the IICPC Codefest. If you believe a submission involves plagiarism, multiple accounts, AI-generated content, or any other form of unfair advantage, kindly fill out the details. Your reports will help us ensure fair competition.

https://forms.gle/yRSBRwWgErpteoXJA

Thank you for your cooperation!

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    4 weeks ago, # ^ |
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    Literally > 95% of the submissions of MNMXPRPAR is GPT generated. ATP shouldn't have considered non-DIV1 participants for the regionals.

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      4 weeks ago, # ^ |
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      The problem with this is a significant chunk of coders who can make it to the top 400 are not active / do not have CodeChef handles, so they had to create one and thus participate in Div4.

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        4 weeks ago, # ^ |
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        If it can still be considered maybe you can put a CF rating bound too.

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When can we expect the final leaderboard?

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Thanks for participating; results of Prelims can be found on https://iicpc.com/prelimsresults