codeforces280 C. Game on Tree（期望）
C. Game on Tree单独考虑每个点对答案的贡献。删除一个点的方案是删除它或者它的祖先，那么对答案的贡献是1depu\frac 1 {\text{dep}_u}depu1#include<cstdio>#include<vector>int n;std::vector<int> g[100005];int dep[100005];void dfs(int u,int fa){ dep[u]=de
