方法：

#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <algorithm>#include <cmath>#include <vector>#define inf 1E9#define maxn 10001using namespace std;vector<int> tree[maxn];int n;int zx=0,minzs=inf;int d[maxn];void dfs(int x, int fa) {	d[x]=1;	int maxzs=0;	for(int i=0; i<tree[x].size(); ++i) {		int to=tree[x][i];		if(to!=fa) {			dfs(to,x);			maxzs=max(maxzs,d[to]);			d[x]+=d[to];		}	}	maxzs=max(maxzs,n-d[x]);	if(maxzs<minzs) {		minzs=maxzs;		zx=x;	}}int main() {	scanf("%d", &n);	for(int i=1; i<=n-1; ++i) {		int x,y;		scanf("%d%d", &x, &y);		tree[x].push_back(y);		tree[y].push_back(x);	}	dfs(1,0);	PRintf("%d %d", zx,minzs);	return 0;}