poj 1655 找树的重心

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#include<map>
#include<set>
#include<cmath>
#include<stack>
#include<queue>
#include<cstdio>
#include<vector>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define mod 998244353
#define pi acos(-1)
#define inf 0x7fffffff
#define ll long long
using namespace std;
ll read()
{
    ll x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
    return x*f;
}
int T,n,ans;
int size[20005],mx[20005];
vector<int>e[20005];
void dp(int x,int fa)
{
    size[x]=1;
    for(int i=0;i<e[x].size();i++)
    {
        int y=e[x][i];
        if(y==fa)continue;
        dp(y,x);
        size[x]+=size[y];
        mx[x]=max(mx[x],size[y]);
    }
    mx[x]=max(mx[x],n-size[x]);
    if(mx[x]<mx[ans])ans=x;
    if(mx[x]==mx[ans]&&x<ans)ans=x;
}
int main()
{
    T=read();
    while(T--)
    {
        n=read();ans=0;
        mx[0]=inf;
        for(int i=1;i<n;i++)
        {
            int u=read(),v=read();
            e[u].push_back(v);
            e[v].push_back(u);
        }
        dp(1,0);
        printf("%d %d\n",ans,mx[ans]);
        for(int i=1;i<=n;i++)e[i].clear();        
        memset(size,0,sizeof(size));
        memset(mx,0,sizeof(mx));
    }
    return 0;
}