Codeforces celebrates 10 years! We are pleased to announce the crowdfunding-campaign. Congratulate us by the link https://codeforces.com/10years. ×

ipaljak's blog

By ipaljak, history, 4 months ago, In English,

Hi all,

it's the most wonderful time of the year as the new season of COCI is getting near :)

Join us on the first round which will be held on Saturday, October 19th at 14:00 UTC.

If you are not familiar with COCI contest format, we encourage you to read the announcement for the new season. Also, this year we have decided to allocate the same number of points to the three hardest tasks and present them in lexicographical order in the problemset.

Feel free to discuss the problems here after the contest ends.

See you on Saturday!

 
 
 
 
  • Vote: I like it
  • +110
  • Vote: I do not like it

»
4 months ago, # |
  Vote: I like it +32 Vote: I do not like it

COCI is love COCI is life

»
4 months ago, # |
Rev. 2   Vote: I like it +42 Vote: I do not like it

I found that all contest held in last year had no "solution"s (that is, editorials are not uploaded).

How is it going this year?

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +24 Vote: I do not like it

    Yeah, we had quite a few complaints about that. We'll give our best to publish this year's editorials on the same day when the round is held.

    Regarding the editorials from the last two seasons, I hope we'll manage to finish and publish all of them during this season.

»
4 months ago, # |
  Vote: I like it +18 Vote: I do not like it

Friendly reminder: the round starts in about 4 hours.

»
4 months ago, # |
  Vote: I like it +36 Vote: I do not like it

So, what do you think about the round and new format of scoring? :)

  • »
    »
    4 months ago, # ^ |
      Vote: I like it -54 Vote: I do not like it

    tasks were cancerous (task 4 for example), and one of the hardest Honi contest...

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +20 Vote: I do not like it

    I think 90 < 110 < 130 is much better because I want some diversity in difficulty. On the other hand, the new subtask system is awesome, and I like the PDF format too.

    • »
      »
      »
      4 months ago, # ^ |
        Vote: I like it +26 Vote: I do not like it

      They were meant to be diverse in difficulty. We assumed zoo < trobojnica < dzumbus. The idea behind the same score was to train our contestants to sniff out the easy tasks since they need that skill for IOI.

      • »
        »
        »
        »
        4 months ago, # ^ |
          Vote: I like it +49 Vote: I do not like it

        I trained a lot with COCI, so phrases like "COCI p5 difficulty" are quite idiomatic to me. Time for a change :)

        • »
          »
          »
          »
          »
          4 months ago, # ^ |
            Vote: I like it +16 Vote: I do not like it

          Really cool to hear the so called "HONI" (COCI) ranking is used by non-Croats. <3

»
4 months ago, # |
Rev. 2   Vote: I like it +23 Vote: I do not like it

Nice contest! I solved a problem identical to the last problem before.

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    One person also mentioned that as a clarification request. He said the same problem was used in Iranian IOI training.

    I actually suggested that problem to be included in last year's COI (which is more important for us than a regular COCI round), but we thought it was too easy and rejected it :)

    I'm sorry if it was a well-known problem for a lot of competitors, but none of us from the scientific committee saw it before and it looks like our competitors didn't know about it either.

    • »
      »
      »
      4 months ago, # ^ |
      Rev. 3   Vote: I like it +18 Vote: I do not like it

      I don't mind it, i find the problem very interesting. Btw. will we be able to submit codes again (I wanna know why my B failed)?

      • »
        »
        »
        »
        4 months ago, # ^ |
          Vote: I like it +8 Vote: I do not like it

        I will try to make that happen. We had some attacks during analysis mode last season so our technical staff is reluctant to allow it this year.

        I'll let you know when/if it happens.

        • »
          »
          »
          »
          »
          4 months ago, # ^ |
            Vote: I like it +10 Vote: I do not like it

          The analysis mode is up and running.

»
4 months ago, # |
  Vote: I like it +31 Vote: I do not like it

The expected solution of dzumbus is $$$O(N^3)$$$ or $$$O(N^2)$$$?

By the way, problem trobojnica was very nice.

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    $$$O(N ^ 2)$$$ is the official solution. Did you pass a $$$O(N ^ 3)$$$ solution or maybe you think it is a $$$O(N ^ 3)$$$ solution :D. The proof of complexity is a key part of the solution.

    • »
      »
      »
      4 months ago, # ^ |
        Vote: I like it +10 Vote: I do not like it

      I am pretty sure that the worst case of my solution is $$$O(N^3)$$$ but it takes full score (with maximum time = 0.06s). Either the testcases are weak or it's simply impossible to distinguish between the quadratic solution and a cubic solution with a very small constant when $$$N=1000$$$.

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +10 Vote: I do not like it

    It was O(n^2). The editorial should be up very soon.

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +33 Vote: I do not like it

    Thanks! Do I get extra credit in Figalli's class for it? :D

»
4 months ago, # |
  Vote: I like it +31 Vote: I do not like it

You can see the results and solutions (with editorial) here.

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +12 Vote: I do not like it

    Some take hours, some take years ... :D

  • »
    »
    4 months ago, # ^ |
      Vote: I like it +10 Vote: I do not like it

    When I try to download the tasks I get "403 Forbidden".

»
4 weeks ago, # |
Rev. 2   Vote: I like it 0 Vote: I do not like it

You can submit all problems except Trobojnica here: https://oj.uz/problems/source/442

  • »
    »
    4 weeks ago, # ^ |
    Rev. 2   Vote: I like it +8 Vote: I do not like it

    You can take code for checker of Trobojnica from the solution of task Checker from round 2.

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

      Nice, now all problems are available, thanks :D