More and More Suspicious Participants in AtCoder Beginner Contests!

Revision en1, by rui_er, 2024-06-01 16:49:23

Hello, CodeForces.

As I can't find any discussion thread in AtCoder, and the announcements of AtCoder contests are also posted here, I decided to post this blog in CodeForces.

Last time (ABC355), I reported a suspicious participant toyuzuko who solved problem ABCD in 51 seconds. They also did the similar thing in ABC354.

This time (ABC356), there are much more suspicious participants.

The average first-AC time (in seconds) of ABC347~ABC353 is in the following table:

Contest A B C D E F G
ABC347 21 45 93 244 177 300 824
ABC348 15 37 72 302 236 495 430
ABC349 23 67 54 116 598 139 634
ABC350 26 47 102 74 240 489 335
ABC351 22 23 106 352 199 122 902
ABC352 27 43 49 90 196 989 188
ABC353 24 79 172 88 206 1161 313
(minimum) 15 23 49 74 177 122 188
(prefix sum) 15 38 87 161 338 460 648

Note that to get first-AC in a problem doesn't require you to solve all the problems before it. You can just skip to the problem you want to get first-AC and manage to solve it at once. So, the least reasonable time to solve a subset of problems is at least the sum of the first-ACs.

To make sure there are fewer exceptions, I will call all the participants who solved any subset of problems faster than the minimum expected time "suspicious".

Now, let's take a look at (some of) the suspicious participants who solved at least 4 problems at last:

Some other participants seem to be suspicious, too. They solved a subset of problems just 10 seconds slower than the sum of the minimum first-AC time in the above table. I think it's impossible to have all the easy problems in a single round, but I didn't list them here, just to make sure there are fewer exceptions.

I guess they probably used some AI to generate the code for them after seeing what happened in ABC355. If my guess is true, I'm impressed with the ability of AI. I'm also worried that more and more people will use AI to generate the code and solve easy problems in the contest. If everyone can solve ABCD by simply copy-pasting AI's code, what's the point of having AtCoder Beginner Contests? Why not just delete ABCD and add some new problems to make an AtCoder Regular Contest?