cdkrot's blog

Comment on Codeforces Round #499 -- interactive problem
By cdkrot, history, 6 years ago, In English

Unfortunately, we had a bug in our interactor of the interactive problem.

The interactor contains the following code:

if (y < x)
    t = -1;
else if(y > x)
    t = 1;
else
    t = 0;
if(!p[q % n])
    t *= -1;
cout << t << "\n" << flush;

This is the opposite to the statement. However, it turns out that this error doesn't causes any harm for solving problem — it actualy just inverts the pattern, selected by judges. This also wasn't noticed during testing, by the same reason — the error is not visible to the user code.

But it may cause unexpected behaviour for hackers -- since they write the pattern themselves.

We are very sorry for this error and decided to do the following:

  • The round will be rated, because very little people (maybe even zero) got affected (the people, who made incorrect hack)
  • If you made a hack, which turned to be incorrect due to the error, we will cancel your  - 50 points and recalculate your rating afterwards. Please PM me if you have such a hack.

We are very sorry again. This is a huge lesson to us to be more attentive.

I hope you enjoyed the round!

  • Vote: I like it
  • +133
  • Vote: I do not like it

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

Auto comment: topic has been updated by cdkrot (previous revision, new revision, compare).

→ Reply
»
6 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Thanks to this post I can downvote the author of awful round and upvote one of the authors of the only good problem in this round.

→ Reply
  • »
    »
    6 years ago, # ^ |
      Vote: I like it +39 Vote: I do not like it

    Please direct your gratitude to 300iq, my contribution to this problem was not very big :), and to VladProg for preparing the test data.

    Also, I hope the other problems weren't that bad, right? =).

    → Reply
    • »
      »
      »
      6 years ago, # ^ |
        Vote: I like it +20 Vote: I do not like it

      Problems were not awful (aside from E), but I do not think they are good as a round

      → Reply
  • »
    »
    6 years ago, # ^ |
      Vote: I like it +53 Vote: I do not like it

    Typical Um_nik at his best xD

    → Reply
    • »
      »
      »
      6 years ago, # ^ |
        Vote: I like it +41 Vote: I do not like it

      I'll take this one as a compliment though I know that it is not :)

      I think that I have a right to express my opinion on round interestingness just like any other CF member. And there is even no personal insults :)

      → Reply
      • »
        »
        »
        »
        6 years ago, # ^ |
          Vote: I like it +19 Vote: I do not like it

        Sure, I understand. I am probably your greatest competitor in complaining race :D

        → Reply