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\n", ans, ans_size);
} return 0;}