Curious Codeforces bug.

Revision en2, by LuaXD, 2015-06-17 08:36:54

Today I was taking part of a virtual Codeforces round ( CF 218Div 2 ). At the time of solving problem C I thought of a Union Find Disjoint Set Data Structure, I coded it and submitted such code. Since it was a virtual round, I immediately got the WA verdict, nevertheless I was sure that the idea was correct. So I made some unimportant changes, submitted again and got the AC verdict.

The thing is, when the round was over, I wanted to know what was wrong with my first submitted code. I opened the log which shows information for each test case to see what happened, but the log info for that case was blank (View the submission 11613966).

I was very saddened to see that the usual WA message wouldn't show up (wrong answer 1st numbers differ — expected: '1', found: '3'). So I decided to copy my code and resubmit.

The resubmission verdict was AC. Both submissions are literally the same. As you can see, one has got a WA verdict and the other has got an AC. This are the two submissions: 11613966 and 11614370

Has this ever happened to any of you? It seems like a very odd bug and I can't figure out why it happened. It is literally a WA verdict for no reason


  Rev. Lang. By When Δ Comment
en2 English LuaXD 2015-06-17 08:36:54 110
en1 English LuaXD 2015-06-17 08:20:38 1324 Initial revision (published)