All 3 last matches made me think again about those questions. In TCO09 Round 1 the hard problem turned out to have a rather strict time limit, and thus my asymptotically correct solution timed out slightly (I believe it ran within 3 seconds) and I had to resubmit, placing only 10th. SRM 436's hard was about fast multiplication of polynomials, and as I don't understand Fast Fourier Transformation good enough to code it and don't have it prewritten, I've resorted to the Karatsuba algorithm and again, my solution was very little over the time limit, so I've spent a lot of time until finally getting it under the time limit (and again, it turned out that this solution was expected to be correct by the problem authors), scored very low and placed only 15th. Today, me failing the medium problem was totally my fault (I couldn't invent the correct solution) - but even if it didn't fail, I would place below Lou because he had a pre-written implementation of the Dinic maximum flow algorithm for the hard problem, and it turned out that one could run that 2500 times under the time limit. This was not possible with the stupid maximum flow algorithm I've used, and thus I had to spent a bit more time implementing a slightly more complex approach.
I still believe that all this happening in a row is just a bad coincidence, and in the long term my strategy has more pros than cons. Next couple of months will show :)