python/TangDou/AcWing/LCA/HDU5452_TanXin.cpp

#include <bits/stdc++.h>
using namespace std;
//没仔细研究为什么贪心是对的
/*
思路：只能切一条生成树上的边，一个比较直观的想法是只切度数为1的点的那条边，然后枚举这个叶子和外面连接的边数即可
*/
const int maxn = 20000 + 7;
#define inf 1e9
vector<int> e[maxn];
int vis[maxn];
int deg[maxn], degg[maxn];
int n, m;
int main() {
    int T, cas = 1;
    scanf("%d", &T);
    while (T--) {
        memset(deg, 0, sizeof(deg));
        memset(degg, 0, sizeof(degg));
        memset(vis, 0, sizeof(vis));
        printf("Case #%d: ", cas++);
        scanf("%d%d", &n, &m);
        for (int i = 0; i < n - 1; i++) {
            int u, v;
            scanf("%d%d", &u, &v);
            deg[u]++;
            deg[v]++;
            if (deg[u] > 1) vis[u] = 1;
            if (deg[v] > 1) vis[v] = 1;
        }
        for (int i = 0; i < m - n + 1; i++) {
            int u, v;
            scanf("%d%d", &u, &v);
            degg[u]++;
            degg[v]++;
        }
        int ans = inf;
        for (int i = 1; i <= n; i++)
            if (!vis[i]) ans = min(ans, deg[i] + degg[i]);
        printf("%d\n", ans);
    }
}