SRM 670 div2 ABC

A Cdgame

Brute force ...

B drbalance

Greedy, at the top of each selection-becomes +, equivalent to all negative +2.

C Treestrat

Consider concentrating on catching a red token, taking the token as the root of the tree, and the subtree of the root of the token in B is not going to go, (the tree is very important)

And there will be more and more nodes that cannot be reached. Find the shortest distance from the node in B to any point V on the tree d[v], when and only if the distance of red token to V is less than d[v]

Before you can go to V. Choose one of the biggest d[v] as the answer to this red token. All red tokens take min.

Code

SRM 670 div2 ABC