POJ 1655 Balancing Act[树的重心]

#include 
#include 
#include 
#include 
using namespace std;
#define N 20010
int s[N], f[N], n, root;
vector g[N];
void getroot(int now, int fa) {
    int u;
    s[now] = 1;
    f[now] = 0;
    for (int i=0; i