Monday, March 27, 2017

A speaking week

Before I switch to the Mar 6 - Mar 12 week, let me correct a mistake in my previous summary: there was in fact a Codeforces round on Sunday, March 5 - but it somehow disappeared from, and my memory turned out to be too short :)

Codeforces Round 403 was the forgotten round (problems, results, top 5 on the left, analysis). Right after the round, I was sure that I needed a lot more debugging to get the last problem accepted - but it turned out that I was super close: the only issue was the often forgotten case of a=0 when solving a quadratic inequality ax2+bx+c<=0. In absence of people solving the last problem during the round it was the speed on the first five that mattered, and V--o_o--V was the quickest - congratulations!

Now we can go back to the subject week. Early on Friday, TopCoder SRM 710 took place (problems, results, top 5 on the left, analysis). Just like the previous round, the hardest problem did not budge, and the round was decided on the first two. Congratulations to al13n on the victory!

And finally, AtCoder held its Grand Contest 011 on Sunday (problems, results, top 5 on the left, my screencast with commentary, analysis). Egor has won the contest thanks to a superior strategy, as he went for the hardest problem in the last minutes of the contest instead of the second hardest. Well done!

I have attempted something new for this round: in addition to the screen content, I've included a camera feed in the screencast, and tried to explain aloud what I'm thinking and doing. I had two big hopes when I decided to do that: that I would actually be able to come up with more polished solutions that take less time to code if I explain them aloud first, and that my mumbling will be interesting to the viewers. The results of the round show that the first hope was likely unfounded, so now I'm really curious about the second one :)

As far as problems go, let me highlight problem E. You are given a huge number n with at most 500000 (decimal) digits, and need to find the smallest number k such that n can be represented as a sum of k numbers with non-decreasing decimal representation (for example, 1157888).

Thanks for reading, and check back soon for the next week's contests!

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