8.1 A group of provincial election
First find the "active site" solution to a problem by the method and then discretized be greedy match. Every time if the current matching point is occupied, try to point the current point in the future occupation squeeze
8.1 Group B Provincial election
First lcp performed according to the relationship of the tree structure, then the value dp is obtained sg tree. The need for sub-tree XOR and optimization.
8.1 Provincial election group C
Discovery process efficiency bottleneck is a consecutive points of edges connected to the node for some bfs sequence. We have optimized this bottleneck can use disjoint-set, you can skip every time period be accessed.