Friday, April 26, 2013

TCO 2B editorial complete, SRM 577

TCO 2B editorial "complete"

You can find it here:

This was a long problem set to solve and explain hence the long time to finish it. I am still going through health scares but I think this one took so long primarily because I needed time to solve it. Specially the medium. Very interesting match, but I wish I would do better in tournaments.

SRM 577 - fail

In SRM 577, I first opened the 500, seemed interesting, but when some coders started to solve the hard problem before there were submissions for 500, I decided to open it. This hard problem really distracted me. I had a very strong feeling there was a flow solution, but I couldn''t put things together.

As usual, when there were 10 minutes before the end of the challenge phase, I opened the 250 points problem. I rushed to code something that was wrong. The bug that distracted me for most of the 10 minutes was that I calculated the expected sum of scores, and not the expected average of scores. When the coding phase finished, I noticed there was still a mistake, I was not handling the possibility that Elly could have a room of different sizes depending on luck.

To solve it, find the probability Elly ends in a room with t or t+1 people (Where t is N/R). For each case, find the average score. Combine results and done.

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