(树的重心) poj 1655

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<cstdlib>
#include<string>
#include<vector>
#define INF 100000000
using namespace std;
vector<int> e[20005];
int n,dp[20005],ans,num;
void dfs(int u,int father)
{
    int maxx=0;
    dp[u]=1;
    for(int i=0;i<e[u].size();i++)
    {
        int v=e[u][i];
        if(v==father)
            continue;
        dfs(v,u);
        dp[u]+=dp[v];
        maxx=max(maxx,dp[v]);
    }
    maxx=max(maxx,n-dp[u]);
    if(maxx==ans)
    {
        if(u<num)
            num=u;
    }
    if(maxx<ans)
    {
        ans=maxx;
        num=u;
    }
}
int main()
{
    int tt;
    scanf("%d",&tt);
    while(tt--)
    {
        scanf("%d",&n);
        for(int i=1;i<=n;i++)
            e[i].clear();
        num=1;
        ans=INF;
        for(int i=1;i<n;i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            e[x].push_back(y);
            e[y].push_back(x);
        }
        dfs(1,-1);
        printf("%d %d\n",num,ans);
    }
    return 0;
}