Codeforces Round #791 (Div. 2)(Codeforces Round #791 (Div. 2))





The signing of AB was relatively smooth. Question a is a problem similar to linear programming. Compared with the solution, I still made it too complicated. In my impression, this similar point appeared in div2c, but it didn’t come out. That linear programming seems to be much more complicated

The C question is stuck again. This time it’s really convinced. The questions are read wrong. I thought about it for more than an hour and thought or as and. Finally, after reading it, the maintenance of the tree array is relatively simple, but there should be a better solution

There are only 10 minutes left for question D. it should be the DP on the graph, or memory search. It has been done less and has little confidence to do it…