POJ 1655 Balancing Act

#include <iostream>
#include <cstdio>
#include <cstring>
#define REP(i, s, n) for(int i = s; i <= n; i ++)
#define REP_(i, s, n) for(int i = n; i >= s; i --)
#define MAX_N 20000 + 10

using namespace std;

int n, u, v;
struct node1{ int v, next; } E[MAX_N << 1];
struct node2{ int sum, cnt; } N[MAX_N];

int head[MAX_N], top = 0;
void add(int u, int v){ E[++ top].v = v; E[top].next = head[u]; head[u] = top; }
int DFS(int x, int last){
    N[x].sum = 1; N[x].cnt = 0;
    for(int i = head[x]; i; i = E[i].next){
        if(E[i].v != last){
            int t = DFS(E[i].v, x);
            N[x].sum += t; N[x].cnt = max(N[x].cnt, t);
        }
    }
    return N[x].sum;
}
int main(){
    int T; scanf("%d", &T);
    while(T --){
        top = 0; memset(head, 0, sizeof(head));
        scanf("%d", &n);
        REP(i, 1, n - 1){
            scanf("%d%d", &u, &v);
            add(u, v); add(v, u);
        }
        DFS(1, 0);
        int ans = 99999999, num = 0;
        REP(i, 1, n){
            N[i].cnt = max(N[i].cnt, n - N[i].sum);
            if(ans > N[i].cnt){
                ans = N[i].cnt; num = i;
            }
        }
        printf("%d %d\n", num, ans);
    }
    return 0;
}