## Monday, February 17, 2014

### This week in competitive programming

There were no contests on weekdays this week, but the weekend was rather busy. On Saturday, the last online round of the Kotlin Challenge took place, top 25 qualifying to the onsite finals in St. Petersburg (problems in Russian, results mostly in Russian, top 5 on the left). Problem B was of the "constructive" type, which is quickly becoming popular in today's contests: instead of optimizing some function, you were asked to provide any answer that fits a given constrainst, with the constraint given with a lot of leeway, allowing many completely different answers. The problem went as follows: you need to print any string with length N consisting of the first K lowercase English letters such that no letter is repeated twice consecutively and no substring is repeated three times consecutively. N is up to 5000, K is up to 26. What approach have you found?

Overlapping with the Kotlin challenge was TopCoder SRM 609 (problems, results, top 5 on the left). I couldn't solve it because of the overlap, so I can't tell you much about the problems. However, it's amazing that Gassa could both qualify for the onsite in Kotlin Challenge and place in top 5 in the SRM - great job Ivan!

On Sunday, the Grand Prix of Udmurtia of the Open Cup continued the run of three consecutive Grand Prix weekends (results, top 5 on the left). The contest was full with problems that nobody could solve, and one of them (problem F) went as follows: you need to write a program that does the same as the given black box. The black box takes a string and outputs a string, there are several examples given, and there's a special problem Q that is the black box: you can send inputs there and learn about the outputs. Not many teams attempted to solve this problem during the contest, but it might be a very interesting task in the upsolving.

And finally, late on Sunday Codeforces ran Rockethon 2014 (problems, results, top 5 on the left). I was too tired to take part, so I can only admire tourist (yet again :)) who managed to win the first place both in the Open Cup and in this contest.

Thanks for reading, and see you next week!