I was an admin of TopCoder for about 4 years. Recently I came back as a competitor and I participated in four SRMs. Here are my performances:

SRM 681 Hard: CoinFlips

It was an easy DP, but I started to implement something stupid and wasted time. When I finished coding around 5 minutes before the end of the contest, the server was slow and I couldn't compile my solution. Though the match was unrated, I should have solved it earlier.

SRM 682 Hard: TheKFactor

My solution failed because of precision errors (in Linear Programming). I should have used long doubles instead of doubles (and passed in the practice room).

SRM 683 Hard: RandomWalkOnGrid

Failed systest because of two (!) stupid mistakes: incorrect array size and integer overflow.

SRM 684 Hard: Permutant

Missed cases with a.size() == 1. Failed systest again.

It's really important to keep participating in TopCoder matches. Now I can't solve anything!