这实际上是一棵树，拓扑排序一下，关键点的流量是所有出水口的数目之和 #define ll int #define vec vector<ll> #define inf 0x3f3f3f3f #define MAX 100005 int n, u, v, ind[MAX], flow[MAX]; vec G[MAX]; int main() { while (cin >> n) { memset(ind, 0, sizeof(ind)); memset(flow, 0, sizeof(flow)); for (in...