POJ 1655 Balancing Act【树的重心】

这个题也很裸了……不多说。

#include <cstdio>#include <cstring>#include <algorithm>#include <vector>using namespace std;#define N 20010int s[N], f[N], n, root;vector<int> g[N];void getroot(int now, int fa) {    int u;    s[now] = 1;    f[now] = 0;    for (int i=0; i<g[now].size(); i++)        if ((u=g[now][i]) != fa) {            getroot(u, now);            s[now] += s[u];            f[now] = max(f[now], s[u]);        }    f[now] = max(f[now], n-s[now]);    if (f[now] < f[root]) root = now;}int main() {#ifndef ONLINE_JUDGE    freopen("in.txt", "r", stdin);#endif    int T, a, b;    scanf("%d", &T);    while (T--) {        scanf("%d", &n);        for (int i=1; i<=n; i++) g[i].clear();        for (int i=1; i<n; i++) {            scanf("%d%d", &a, &b);            g[a].push_back(b); g[b].push_back(a);        }        f[0] = n;        getroot(1, root=0);        int cnt = 0;        for (int i=1; i<=n; i++) if (f[i] == f[root]) {            root = i; break;        }        printf("%d %d\n", root, f[root]);    }    return 0;}