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
What a beautiful language C++!
When there is no checker comment in the report, you can assume something is wrong on the judges' side, and report it to the judges directly. Of course, it does not still mean your solution is right in the general case.