THE_THUNDERSTORM_BEGINS's blog

EXSTREAM CHEATING IN LAST ROUND D
By THE_THUNDERSTORM_BEGINS, history, 11 hours ago, In English

hello codeforces

yesterday i noticed that someone from my friends solved problem D in 8 minutes.

well this friend is known in our telegram training group to be a cheater.

i refused that fact cuz there is no direct proof.

while i was looking at his code i noticed that some code was copied and pasted 3 times in different functions doing nothing.

i knew that was not normal , so i needed a proof now.

so i decided to look at problem D solves and was suprised that so many solutions are alike in a way, but different only in variable names, and some of them were in a straight one line of code , but the same idea over and over.

you can check some examples

308151686 308117651 308160744 308153550 308165846 308152360 308142455 308171609 308166500 308167550 308158553 308146140 308144552 308158580 308144531 308170236 308171447 308138274 and best for last 308165802

you can notice the large similarity between them,,

most of them were submitted at the near end of the contest,

these acts are not acceptable in this community, so many coders leave CP because others are cheating and he is getting negative delta over and over while not cheating.

i would like to notice MikeMirzayanov to these acts.

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9 hours ago, # |
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Auto comment: topic has been updated by THE_THUNDERSTORM_BEGINS (previous revision, new revision, compare).

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9 hours ago, # |
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I feel some of the solutioms havent used mod correctly

Like they have done (a * b) mod instead of (a mod * b mod) mod

If this can give some overflow, lets try hacking them ?

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    9 hours ago, # ^ |
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    its unhackable btw since both a and b will always be below mod

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      9 hours ago, # ^ |
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      i tried to find a hack but didnt even understand their approach , they are starting from leaves rather than the root .

      also they somehow understand dp alot to get some relation like this .

      also through the problem i did not notice that

      p(i)<i

      in the input

      what a coincidence that they all noticed that

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        7 hours ago, # ^ |
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        I'm not sure how can you not start from leaves, look 308132441 my solution, it is more direct. But looking at how gods of DP solve it, it really is obvious that for every depth you add children of others of same depth and subtract own, so can reduce it to one multiplication.

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7 hours ago, # |
← Rev. 7   Vote: I like it +1 Vote: I do not like it

Also these:

awoo

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27 minutes ago, # |
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exstream is my new favourite word

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