树形DP poj1655

#include <iostream>
#include <cstring>
#include <cstdio>

using namespace std;

int num;
int head[20010];
int dp[20010];
int val[20010];
int n;

struct edge
{
    int fro,to,next;
}e[40100];

void addEdge(int _fro,int _to)
{
    num++;
    e[num].fro=_fro;
    e[num].to=_to;
    e[num].next=head[_fro];
    head[_fro]=num;
}

void dfs(int x,int from)
{
    if(dp[x]!=0)
        return;
    dp[x]=1;
    for(int i=head[x];i!=-1;i=e[i].next)
    {
        int sum=0;
        int v=e[i].to;
        dfs(v,e[i].fro);
        if(v==from)
            continue;
        val[e[i].fro]=max(val[e[i].fro],dp[v]);
        dp[e[i].fro]+=dp[v];
    }
    val[x]=max(val[x],n-dp[x]);
}

int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        scanf("%d",&n);
        num=0;
        memset(head,-1,sizeof(head));
        memset(dp,0,sizeof(dp));
        memset(val,0,sizeof(val));
        int a,b;
        for(int i=0;i<n-1;i++)
        {
            scanf("%d%d",&a,&b);
            addEdge(a,b);
            addEdge(b,a);
        }
        dfs(1,0);
        int ans=1<<29;
        int se;
        for(int i=1;i<=n;i++)
        {
            if(val[i]<ans)
            {
                ans=val[i];
                se=i;
            }
        }
        cout<<se<<" "<<ans<<endl;
    }
    return 0;
}