Facebook Hacker Cup 2019 Round 2 Screencast

Screencast of Hacker Cup Round 2. This round is where it gets serious: only 200 people get to advance. My results are below:
I came in 86th with the first three problems correct, time penalty 2:19:29. For the fourth problem, I had a solution written, but it was failing the large sample case and I didn't have time to debug.

[@devarajakhilmatta320]

Hey, I'm a beginner, can you explain why you are checking with the first bit of (x+y) every agent, i just want to know the reason behind it. It would be great help if you can, Thank you.

[@SnapDragon128]

It's just a simple way to test whether (x,y) is a black or a white checkerboard square. Problem A just boils down to a parity invariant: notice that no matter how the agents move, their pattern of black/white squares can't change.

[@НурбекЭркулов-ъ3г]

Did you try codeforces rounds ?

[@SnapDragon128]

Afraid not; I haven't been competing in regular contests for a long time. Judging at the ICPC Finals is my only link to the contest community these days.