I think I found a bug about hacking. I did 2 successful hacks during Codeforces Round #115, but after contest it showed there's only one hack. The other one is 'ignored'. But I think it should be a successful hack.
38336 Apr 14, 2012 1:25:35 PM sillycross Skyly A — Robot Bicorn Attack Ignored
The victim's submission history:
00:13:50 Accepted [pretests] → 1532327
01:39:54 Accepted [final tests] → 1535677
And submission 1532327's status
By Skyly, contest: Codeforces Round #115, problem: (A) Robot Bicorn Attack, Hacked, #
Obviously the submission done in 00:13:50 was hacked by me ( I'm the only one who hacked this solution ) . But the hack was ignored.
I think it was caused by my another hack using the same input.
38343 Apr 14, 2012 1:30:08 PM sillycross helThazar A — Robot Bicorn Attack Successful hacking attempt
I knew that the codeforces judge would ignore same hacking inputs and only keep the last one. But it was obviously that hacking attempts of same inputs shouldn't be ignored when they were used for different victims. I think it should be a bug. This bug can be serious because when we found a very strong test data it's quite usual to use it to hack different victims. I hope this bug can be renovated soon.