题目链接 Balancing Act
就是求一棵树的重心,然后统计答案。
#include <bits/stdc++.h> using namespace std; #define REP(i,n) for(int i(0); i < (n); ++i) #define for_edge(i,x) for(int i = H[x]; i; i = X[i]) const int INF = 1 << 30; const int N = 100000 + 10; int H[N << 1], E[N << 1], X[N << 1]; int T, et, n, x, y; int son[N]; int ans_size, ans; inline void addedge(int a, int b){ E[++et] = b, X[et] = H[a], H[a] = et; E[++et] = a, X[et] = H[b], H[b] = et; } void dfs(int x, int fa){ int sn = 0; for_edge(i, x){ int u = E[i]; if (u != fa){ dfs(u, x); son[x] += son[u]; sn = max(sn, son[u]); } } ++son[x]; sn = max(sn, n - son[x]); if (ans_size > sn || ans_size == sn && ans > x){ ans_size = sn; ans = x; } } int main(){ scanf("%d", &T); for (; T--;){ ans_size = INF; ans = INF; memset(H, 0, sizeof H); memset(son, 0, sizeof son); et = 0; scanf("%d", &n); REP(i, n - 1){ scanf("%d%d", &x, &y); addedge(x, y); } dfs(1, 0); printf("%d %d ", ans, ans_size); } return 0; }