poj 1655 树的重心

#include<stdio.h>
#include<string.h>
#include<vector>

using namespace std;

vector<int > mp[20005];
int num[20005],vis[20005],dp[20005];
int n, point ,minn;
void init()
{
	for(int i =0 ;i < 20005; i++)
	mp[i].clear();
}

int Max(int a,int b )
{
	return a>b?a:b;
}

int dfs(int x)
{
	vis[x] = 1;
	num[x] = 1;
	for(int i = 0;i < mp[x].size(); i++)
	{
		if(!vis[mp[x][i]])
		{
			num[x]+=dfs(mp[x][i]);
			
		}
		dp[x]  = Max(dp[x],num[mp[x][i]]);
	}
	dp[x] = Max(dp[x],n - num[x]);
	if(dp[x]  < minn)
	{
		minn = dp[x];
		point = x;
	}
	
	return num[x];
}

int main()
{
	int tot ,a ,b;
	while(~scanf("%d",&tot))
	{
		while(tot--)
		{
			minn = 200000;
			scanf("%d",&n);
			init();
			for(int i =0 ;i < n-1; i++)
			{
				scanf("%d%d",&a,&b);
			    mp[a].push_back(b);
     			mp[b].push_back(a);
			 }
			 memset(dp,0,sizeof(dp));
			memset(vis,0,sizeof(vis));
			dfs(1);	

		    printf("%d %d\n",point,minn);	
		}
	}
	return 0;
}