poj 1655 树形dp

#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;

struct node
{
int to,next;
}A[40010];
int tot,list[20010],mark[20010],n;
int add(int a,int b)
{
A[++tot].to = b;
A[tot].next = list[a];
list[a] = tot;
return 0;
}
int dp[20010],subtree[20010];
int max(int a,int b)
{
return a>b?a:b;
}
int dfs(int point)
{
mark[point]=1;
int b;
int k=list[point];
if(k==-1) {dp[point]=n-1;subtree[point]=0;return 0;}
for(;k!=-1;k = A[k].next)
{
b = A[k].to;
if(mark[b]) continue;
dfs(b);
subtree[point]+=subtree[b]+1;
dp[point]=max(dp[point],subtree[b]+1);
}
dp[point]=max(dp[point],n-subtree[point]-1);
return 0;

}
int main()
{
int i,j,T;
scanf("%d",&T);
while(T--)
{
scanf("%d",&n);
tot=1;
memset(list,-1,sizeof(list));
memset(mark,0,sizeof(mark));
for(i=1;i<n;i++)
{
int a,b;
scanf("%d%d",&a,&b);
add(a,b);
add(b,a);
}
memset(dp,0,sizeof(dp));
memset(subtree,0,sizeof(subtree));
memset(mark,0,sizeof(mark));
dfs(1);
int Min=3000000,k;
for(i=1;i<=n;i++)
if(dp[i]<Min)
{
Min=dp[i];
k=i;
}
printf("%d %d\n",k,Min);
}
return 0;
}