MagentaCobra's blog

By MagentaCobra, history, 3 years ago, In English

So today I struggled to solve 1527B2 - Palindrome Game (hard version) officially today. I ended up getting wa tc 2, which seems pretty common at first. However, after the contest finished, I noticed that the ONLY reason why my solution wasn't correct was because I said "TIE" instead of "DRAW"

116825145 (The WA officially) 116845616 (AC after the contest)

I don't understand why problem writers can't spend time to include complete samples? I've written a few official CF rounds myself, and this is definitely not OK. Samples should always include all possible types of output. You can't argue the case that not including a "DRAW" case in samples will give away the problem either, because it clearly doesn't (001 is a trivial "DRAW" case).

Please do better next time. I'm super disappointed that none of the problem writers, the coordinator, or even any of the testers pointed this out. We look forward to these contests every time they happen, and it really sucks when your performance is ruined by a silly thing like this.

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3 years ago, # |
  Vote: I like it +165 Vote: I do not like it

Don't you think that it is your own fault that you didn't read the statement properly.

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3 years ago, # |
Rev. 5   Vote: I like it +20 Vote: I do not like it

There's only 1 case (apart from very obvious all-1) when there's draw. Revealing that would have spoiled the problem. There's no case other than 001 that'd be draw. Obviously you can say examples like 11010, 1010111 etc but they are essentially the same.

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    3 years ago, # ^ |
      Vote: I like it +60 Vote: I do not like it

    They wouldn't need to reveal that there's only one case where there's a draw, only that there is some case where there's a draw.

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      3 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      many times people try to make hypothesis from samples(think in direction provided by samples) and some times it turns out to be the solution.

      From today's problem A samples we can make hypothesis that answer would be one less than some power of 2. Also after seeing the samples of problem B2 i started to think in direction that Alice will win in most of the cases (though i messed up with corner cases).

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        3 years ago, # ^ |
          Vote: I like it +25 Vote: I do not like it

        I don't see how the fact that a sample exists where the answer is a draw and that sample is "001" should be expected to lead someone to the conclusion that there's only one class of draw cases. The samples that the problem actually included were just as simple as "001". We shouldn't worry about scenarios where certain samples might point someone in a certain direction to the extent that we make the samples significantly less robust because of it.

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    3 years ago, # ^ |
      Vote: I like it +21 Vote: I do not like it

    I am not sure about this, but couldn't they have given '111' as a case for DRAW and removed It is guaranteed that the string s contains at least one '0' ? Correct me if I am missing something.

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

There is only one case of draw though. So, it isn't possible. However, they should've blocked the outputs. That's something setters should work on, they should try to highlight the key statements

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

Come on, that's your fault

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

I think the problem statement was pretty clear, actually.

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3 years ago, # |
  Vote: I like it +25 Vote: I do not like it

it really sucks when your performance is ruined by a silly thing like this.

what made you think beforehand that you need to print "TIE" when none wins ? It means you didn't read the question properly which is itself silly.

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Wait sorry like how is not revealing a small amount of information about the problem's solution somehow more important then having decent test cases? If a problem's easier than usual this is far less frustrating then having crappy samples.

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    3 years ago, # ^ |
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    Like contests in general should prioritize being actually enjoyable over being super merit-based.

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3 years ago, # |
Rev. 2   Vote: I like it 0 Vote: I do not like it

I think there should have been DRAW case as it will only make it better. But it doesn't making quite sense printing TIE when not even mentioned anywhere.