## Thursday, April 30, 2015

### A week where Open Cup ends

Another very busy weekend in competitive programming started with Russian Code Cup Qualification Round 2 (problems in Russian, results, top 5 on the left). The current ACM ICPC World Champions have occupied the two top spots, and big congratulations to Pavel for solving all problems!

TopCoder Open 2015 Round 1B took place later on Saturday (problems, results, top 5 on the left). Since all coders with "red" rating that have participated in at least one SRM in 2015 got automatic promotion to Round 2, the top of the scoreboard consistent exclusively of somewhat retired contestants. Seyaua has overcome several coders with much higher rating to claim the victory - great job!

Open Cup 2014-15 Grand Prix of East and West happened on Sunday (results, top 5 on the left). The same problemset will be used for an upcoming online contest at Timus, so I don't want to go into detail about the problems - will do my best to come back to them later.

Codeforces Round 300 wrapped up the weekend's competitions (problems, results, top 5 on the left). With 8 problems in the round, it wasn't easy to get them all, and thus people who opted to spend more time on hacking were rewarded - congratulations to Bruce on squeezing out the first place! I've decided to do both hacking and solving the last remaining problem, and in the end was not so successful in both directions. There's a popular Russian saying to that respect, which the Internet suggests sounds as "between two stools you fall to the ground" in English :)

Here's the problem I couldn't get during the round: you're watching a robot that performs a program of given length L in an infinite cycle on a cartesian plane. Each of the L steps of the program is a move in one of four cardinal directions, and after the last step the robot continues with the first step again. You're given the locations of the robot at different times (more precisely, at most 105 times, each time is at most 1018), and need to restore at least one possible cyclic program of length L that would lead to the robot appearing in given locations at given times, or report that there isn't any.

Another big event took place on the weekend: the 24-hour programming session with live video and commentary by Mimino (event page), where he explained solutions to Project Euler problems as he solved them. Only the first 4 hours of the recording seem to be available now.

Thanks for reading, and check back next week for the solutions of the problems I mention here and in last week's summary!