Morphy's blog

CC April Long 2021
By Morphy, history, 4 years ago, In English

We invite you to participate in CodeChef’s April Long Challenge, this Friday, 2nd April, from 15:00 IST onwards.

The contest will be open for 10 days, i.e., until 12th April. I challenge you to get perfect score in 5h.

Gameskraft and Amazon are the official contest recruiters! Gameskraft is looking for Javascript and Frontend Developers from CodeChef and Amazon is hiring fresher and experienced programming talent for SDE 1, SDE 2, and SE roles across India.

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:

Prizes:

The winners will receive certificates and CodeChef laddus with which they 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.

See you in the ranklist!

  • Vote: I like it
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  • Vote: I do not like it

Comments Comments (21)
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4 years ago, # |
  Vote: I like it +150 Vote: I do not like it

I challenge Codechef to complete all MOSS runs of past long challenges in next 17 hours .

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4 years ago, # |
  Vote: I like it +59 Vote: I do not like it

As a problem setter, I assure you that the problems are interesting and challenging.

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4 years ago, # |
  Vote: I like it +41 Vote: I do not like it

I am really enjoying this month's long challenge. In particular, Pair Flips took me a huge amount of time and refinement and was satisfying to solve.

However, a question: are test cases being added / modified mid-contest? Is this normal?

E.g., on Tree Perm, my Pypy3 solutions only scored 40 points at submission time (TLE on some harder cases). I translated my code into C++ and passed everything in 0.7 seconds. Looking back today, it appears my Pypy3 solutions have been retroactively modified to receive 70 points (this is irrelevant), and my C++ solution is still 100 points but now takes 1.28 seconds.

It seems a bit odd that solution judging is changing during the contest. Is this some sort of hacking phenomenon? It would be nice to know if new cases are added, particularly if it means that solutions receive fewer points.

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    4 years ago, # ^ |
      Vote: I like it -17 Vote: I do not like it

    Yes they add tests mid-contest sometimes because many participants copy each other's codes. For e.g., in the January challenge, one guy posted the solutions on YouTube and over 5000 participants copied his solution. But his solution was TLEing for larger tests, so they added larger test cases during the contest.

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      4 years ago, # ^ |
        Vote: I like it +5 Vote: I do not like it

      Interesting. Thanks, helpful info.

      I think it would be helpful to be notified if your solution's judgement changes, though. It hasn't affected me so far, but if (for example) it turns out that I need to refine an algorithm some more, it would be helpful to know.

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    4 years ago, # ^ |
    ← Rev. 6   Vote: I like it 0 Vote: I do not like it

    Initially in TreePerm some files in subtask 2 and 3 has TL configured as 1s and some files had TL configured as 2s. TL of all tcs in subtask 2 and 3 was raised to 2s. Non AC solns were rejudged on this problem. An announcement regrading this rejudging was also made.
    No new tcs were added after the contest started.

    In recent past I'm only aware of this incident when tcs were modified during the contest.

    Whatever op is saying regarding practice of adding tcs mid contest inspired by youtube influencers is just random bullshit.

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Thank you — that sounds reasonable. I see the announcement now, although I would still suggest perhaps some sort of notification system if people's scores actually change. It's quite possible people might consider their participation complete in a contest and not revisit it.

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      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it +32 Vote: I do not like it
      • Whatever this unrated acc is saying regarding practice of adding tcs mid contest inspired by youtube influencers is just random bullshit.

        Ok, but this is not just another alt account made only for random shitposting.

      • In recent past I'm only aware of this incident when tcs were modified during the contest.

        YOU are not aware doesn't mean it never happened. Can you explain what is this ?
        CC Jan Long Challenge 2021 was from 1st Jan to 10th Jan.

      • To back my claim that this was done after the solution video posted on YouTube

        See this. Link to the blog. Now, maybe it was just co-incidence that they added one extra test out of the blue after this blog was posted. And maybe it was another co-incidence that the test was added to only that problem whose solution was leaked. And maybe it was yet another co-incidence that after the test was added and solutions were re-judged, only those participants' solutions failed who copied the code from that guy's video (that is approx. 4000 solutions' verdict changed from AC to Partially Correct). But finally, even if I am wrong, at least you are aware of some incident that you were not aware of.

      • Conclusion: Before using the words like BullShit and stuff on a public platform, you must have something to back whatever you are saying. Otherwise this is just codeforces, you may face real problems in real life. This is not the first time that I have seen you behave like an arrogant dumbhead. Not only on codeforces, but on other platforms (like discord), you behave like you were the one who taught CP to tourist. But you still can be a nice person and talk gently to everyone who are asking something and genuinely want to learn. Just TRY it, it will happen. Best wishes.
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        4 years ago, # ^ |
        ← Rev. 2   Vote: I like it +2 Vote: I do not like it

        No, test cases were added because they were weak. It has nothing to do with cheating.

        Also, their admin mentioned the reason in this blog-

        https://discuss.codechef.com/t/behind-the-scenes-january-long

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          4 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          How will the problem setters know that the test cases are weak ? Even on codeforces, the setters get to know about weak tests only if there are lot of hacks. And if they knew the test cases are weak, why did they include the "strong" tests mid-contest, and not before the starting of the contest. No one can know beforehand that the tests are weak. If they know, why would they leave it weak. At least try to say something logical.

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            4 years ago, # ^ |
              Vote: I like it +27 Vote: I do not like it

            Lol, they got to know the test cases were weak because non optimal approaches were passing. As simple as that. They didn't include strong test cases before because they didn't anticipate such non optimal approaches.

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4 years ago, # |
  Vote: I like it +15 Vote: I do not like it

Congrats to the winners!

Div 1.

  1. RGB_ICPC2
  2. oilhun
  3. busamate
  4. akee
  5. demoralizer
  6. CoderAnshu
  7. chaemon

Div 2.

  1. dotaveterans
  2. xceptional
  3. dorijanko
  4. noimi
  5. dioji
  6. suyashc222
  7. krp1999

Text editorials | Video editorials

Behind the scenes

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +43 Vote: I do not like it

    Wow it feels great to see a pupil get global rank 6 in div2. I have no words. Such clever modification of codes. But if one carefully observes and analyze his code one can easily conclude that he copied from youtube.

    Shame on you man suyashc222. People like you are ruining long challenges for others.

    JaySharma1048576 since you are the author please see his submissions too once you get time. He modified his code so nicely.

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      4 years ago, # ^ |
        Vote: I like it -53 Vote: I do not like it

      If you think that I have copied then I would have not solved Chef and Pair Flips for 50 points. It is solved by only 2 of them for 50 points.

      Before saying someone has copied first try to check different approaches applied, attempts, date and time of the solution that person has submitted.

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      4 years ago, # ^ |
        Vote: I like it +14 Vote: I do not like it

      I request the codechef admin to take serious actions against these cheaters!

      For how long will you allow such kind of activities on your platform.

      Also please stop calling companies for recruiting via long challenges. You are wasting precious time of yours and also of these companies.

      These recruitment challenges are the root cause of the ever increasing cheating in this platform.

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    4 years ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    Thanks !! The problemset was really great.

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    4 years ago, # ^ |
      Vote: I like it +9 Vote: I do not like it

    Does Codechef have changed it's policy against cheaters?

    I think Codechef has unofficially allowed cheating.

    After March long challenge, I had reported few cheaters. I had reported it in codechef discuss and even mailed to codechef with proofs. But codechef has taken no action till date and result is that same guy cheated again. He ended up at Global rank 9 in Div 2. This guy is rajanarora1999

    He has two codechef ids: rajan9353 and rajan0909.

    I don't want to waste much time on proving he is cheater as Codechef doesn't care.

    Just see his submissions of TREEPERM : Submission of rajan9353 Submission of rajan0909

    Remove useless functions from code template of rajan0909, both codes are same (just variable names are changed).

    Also notice 

    for(int i=1;i<100000;i++)
    {
        if(i==2)
        break;
    }

    This loop is there 29 times in rajan0909's submission.

    Also,

    while(true)
    {
        int a;
        a++;
        break;
    }
}

    This loop is there 29 times in rajan9353's submission.

    I see only one reason for these loops i.e. To avoid being caught by MOSS (Which I don't think is run by codechef anymore).

    Also rajan9353 doesn't belong to Jadavpur University which he mentioned in his profile. I have screenshots where he filled different university.

    This is the link to my previous comment on his cheating in case anybody still have some doubts..

    I don't think any action will be taken against him as codechef doesn't take action even after mailing all proofs. I don't understand what codechef is doing. Codechef is unable to catch cheaters and when somebody reports by mail then also codechef doesn't take any action.

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4 years ago, # |
  Vote: I like it +11 Vote: I do not like it

I participated in a Long Challenge after an year thinking the cheating situation would have gotten better. How naive of me. I was feeling dumb because people rated much lower than me were solving way better than me, and now I find solutions of problems were leaked on Youtube. They really need to rethink over this Long format, its pretty useless and demoralizing as it is now.

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    4 years ago, # ^ |
      Vote: I like it +13 Vote: I do not like it

    Codechef under DIRECTI >>>>>>>> Codechef under Unacademy

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