The problemsetters received a lot of flak for the tight time limits. I have not solved the round myself, so I can't offer any firsthand experience. However, I found it quite impressive that three different coders were complaining about having to squeeze their solutions only to learn that the have bad asymptotic complexity (1, 2, 3 — thanks a lot to dorijanlendvaj for investigating those!).problems, results on the left, stream recording, analysis). The problems were significantly easier compared to Semifinal 1, with a relatively standard easy, a unique but not very hard medium, and a hard which was mostly solved by printing out the nimbers for small inputs and figuring out a pattern. Solving all three problems was enough to advance without any additional concerns; Egor and uwi solved two each, and Egor got ahead thanks to uwi's resubmit and his own successful challenge.
- Add one to any number. This operation costs 1.
- Subtract one from any number. This operation costs 1.
- Add one to any contiguous segment of numbers. This operation costs C.
- Subtract one from any contiguous segment of numbers. This operation costs C.