ace5's blog

By ace5, 6 weeks ago, translation, In English

Today I got this message:

Spoiler

When looking at the solutions of the listed participants on the problem 1951B I saw that all these solutions completely (or with a change of variables) same as mine, so it's not just a coincidence, solutions copied from mine. Since I didn't give my solution to anyone, and didn't keep the code publicly available, this could only happen if one of the participants blocked this task, copied my code, and sent it to the others.

Indeed, it turns out that in my room only one participant blocked task B — _Untrackable_(the nickname speaks for itself). He blocked this task at 1:44, and if you look at the submissions of participants from the list, you can see that many of them earlier sent code for this task that was completely different from mine (some even in other languages!), but all of them at approximately 1:55 (after he blocked this task), sent almost exactly my code.

This method of cheating at contests allows the person who sends solutions to everyone to remain unpunished, and all the punishment goes to another honest participant.

Please look at this problem, MikeMirzayanov.

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6 weeks ago, # |
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Hi, indeed such leaks happen sometimes. I want to assure you that participants whose code was leaked by this way never get punished (and you can see it, as your submissions were not skipped) but it's not always obvious who leaked it.

Thanks for the report, we will unrate _Untrackable_ from this contest.

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    6 weeks ago, # ^ |
      Vote: I like it +48 Vote: I do not like it

    Hi, so the last sentence in the message isn't true (it says I could get banned)?

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      6 weeks ago, # ^ |
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      You won't be punished if it is your first time.

      P.S: I didn't mean he's cheated, I just meant he won't be punished if he's innocent

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      6 weeks ago, # ^ |
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      You won't get banned for leaking through hacks, don't worry.

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    6 weeks ago, # ^ |
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    Why not just leave first unique solution, and discard all the copies?

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      6 weeks ago, # ^ |
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      I guess there are cases where the original solver also leaks the solution deliberately, in such cases it is fair to punish all of them.

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        6 weeks ago, # ^ |
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        Maybe it's fair, but: 1) it's hard to tell if they really had malicious intent, or just are ace5. 2) if every copied code will be guaranteed to not count, no one will want to paste it, problem solved, no?

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6 weeks ago, # |
  Vote: I like it +165 Vote: I do not like it

IMO the best solution to this problem is to either disable hacks completely or have a separate short hacking session after the contest. Codeforces is the only popular competitive programming website where solutions can be compromised mid-contest very easily.

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    6 weeks ago, # ^ |
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    have a separate short hacking session

    This is reinventing TopCoder I believe.

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      6 weeks ago, # ^ |
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      TopCoder was right all along (maybe even the weak tests are good).

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        6 weeks ago, # ^ |
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        Agreed. The added push to reason about your code and the chance to have a good shot at hacking was definitely enjoyable!

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    6 weeks ago, # ^ |
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    ex-ICPC

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      6 weeks ago, # ^ |
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      I guess not every contest is in ex-ICPC rules

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    5 weeks ago, # ^ |
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    i feel like hacking should just be completely removed.

    There is no current purpose to it, 99% of hacks are not some smart case tripping up wrong greedies but a string hashing hack or umap hack etc.

    if you have rooms (even after contest), it is a matter of luck (imagine losing 1st place to this, yes it has happened), if you do not have rooms, it is even more a matter of luck and just finding the wrong guy fast.

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6 weeks ago, # |
  Vote: I like it -226 Vote: I do not like it

i was giving today contest and i see the notification. i was shocked to see so many of u blindly aggreing him.** is there any proof that he had not cheated ? just because he is high rated u are agreeing to him blindly . he may have leaked it ? if u see my past contest i only solve div2 c,d,e for practicing . i am not interested in rating ( u cann see it from my past contest i had solve c but then start solving d) if i have to cheat then i would i have easily crossed the pupil mark atleast.

i give contests only for fun . i did not know how blind u guys are , just because a high rated user start saying senseless thing . he may have given solution to his friends etc. and u guys agree to his statments.** he already know low rated user are scape goats for this senseless thing.

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    6 weeks ago, # ^ |
      Vote: I like it +74 Vote: I do not like it

    Saying "I don't even care about rating" is a really bad excuse. It's clear you don't care about rating, in fact you don't care about CP at all, but perhaps you do care about the money other cheaters pay you to give them solutions.

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      6 weeks ago, # ^ |
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      He doesn't care about didgnity as well

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      6 weeks ago, # ^ |
      Rev. 2   Vote: I like it -79 Vote: I do not like it

      If u had some basic level of general thinking then only read the below part else u can downvote and comment senseless paragraphs like u are doing

      IF I HAVE TO GET MONEY FROM CHEATERS THEN I WOULD HAVE SOLVED EVERY CONTEST FROM A THEN B THEN C ..GOING ON .. I WOULD NOT HAVE SOLVED QUESTIONS RANDOMLY.I WOULD HAVE SOLVED QUESTIONS IN A LINEAR MANNER( NOW PLSS DON'T COMMENT WHY IN LINEAR MANNER,I HAD GIVEN WARING ABOVE- IF U HAVE BASIC LEVEL OF GENERAL THINKING).

      I AM NOT FOOL TO INVEST 1 HR ON PROBLEM D JUST TO GET WA 2 INSTEAD OF SOLVING A,B,C TO GET MONEY IN EVERY CONTEST

      If u have any valid reason to tell me I got money from cheaters then plss reply I will be happy to know abt it . If u had seen my sumbission in the contest i had solved c then tried b then a ..if I have to get money i would easily fast solved a and started selling solution Before putting blame on some one. Have some basic level of general thinking

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        6 weeks ago, # ^ |
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        thats just cringe

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        6 weeks ago, # ^ |
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        cope imo

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        6 weeks ago, # ^ |
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        Actually, solving problems in different from alphabetical order is sometimes a clever thing. If problem A costs 500 points, problem B costs 1000 points but you expect to spend 7 minutes on A and 10 minutes on B, better start with B.

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          6 weeks ago, # ^ |
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          But if I am concerned about selling solution to CHEATERS and earning money then I would have start from a . As we never know the difficulty level of each question. Some time even b is harder and of rating 1700.

          U may have seen many cheaters wo sell solution start from a .

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            6 weeks ago, # ^ |
            Rev. 3   Vote: I like it +35 Vote: I do not like it

            No, if a person wants to cheat, it also might make sense to solve problem D before A, B, C. This way they can get a competitive advantage in the cheater market. A cheating acceptor can get A, B, C solutions from one cheating donor and D from another.

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              6 weeks ago, # ^ |
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              Harvard wants to know your location.

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              5 weeks ago, # ^ |
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              I solved D before A,B,C in div3/4s and regret it because the penalties add up to the point where I became lower ranked than the one who does A,B,C first and D slowly.

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                5 weeks ago, # ^ |
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                Yes, solving the problems in different order is not always profitable. It is profitable when a problem is harder than one of the next ones, or when it's easier but not as much easier as it is cheaper.

                In your case probably D took too much time to start with this problem. Also note that you get tired after solving a hard problem earlier but still need to solve those easy problems.

                You can train this exact aspect here: https://codeforces.com/blog/entry/58256

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                  5 weeks ago, # ^ |
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                  Sorry for the downvote, it was by accident. I do want to upvote.

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                  5 weeks ago, # ^ |
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                  Never mind :)

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        6 weeks ago, # ^ |
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        but who would pay you for a solution to ABC?

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    6 weeks ago, # ^ |
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    womp womp

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    6 weeks ago, # ^ |
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    bruh playing ratism card LMAO

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6 weeks ago, # |
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This whole situation seems really funny to me, because cheater is obvious here and so many coincidental events must happen to make it possible.

At first he is the only person who blocked his submission in the room, that is already pretty improbable.

Secondly out of all participants in his room, he picked the most (or one of the most) higher rated one, but not only that, one of the known members of community. If he picked some low rated user, I am pretty sure that such person would not make investigation this big.

Then for some reason he submitted this problem really late in the contest and if, let's say, he blocked his submission at 0:15 and copied submits started at 0:30, it's fine. But 1:44 and 1:55 is not.

And finally, he did not change any of the code. It is second problem in the contest and changing even a few lines of code should be enough.

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    6 weeks ago, # ^ |
      Vote: I like it +16 Vote: I do not like it

    Theoretically, if I were a master and I wanted to sell my code, it would be pretty easy to make this happen. Maybe after 1:45 I saw someone locked B, so I would have an excuse when the codes coincide, and farm some positive contribution.

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6 weeks ago, # |
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this exact situation was brought up before https://codeforces.com/blog/entry/108122

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6 weeks ago, # |
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is it possible to block any task during the contest? i don't understand this part.

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6 weeks ago, # |
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Bro, why isn't anyone viewing from this POV: I'm a master, who is very trusted through the community and people will believe me, I wanna make some money.
I'll solve div2 problems abcde, and when a person from my room locks that problem, I'll start selling it, so if I got code coinciding, I can just blame that random poor guy.

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    6 weeks ago, # ^ |
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    Bro, why isn't anyone viewing from this POV: I'm a hard-stuck newbie who is totally and completely unsucessful in life so I dropped down to cheating and selling solutions by locking problems and stealing other people's codes. Then, when I was exposed, I used my shitty alt to try and blame the other person, who's obviosly innocent, which totally worked! (spoiler: it didn't)

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6 weeks ago, # |
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I guess seeing the room from Untrackable's point of view would make some sense? Maybe he opened only one code (which would be very suspicious)?