bzoj1131 Sta

#include<iostream>
#include<cstdlib>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<cstring>
#define ll long long
const int MAXN=1000010;
using namespace std;
int n,a,b;
int first[2*MAXN],to[2*MAXN],next[2*MAXN],cnt;
inline void add(int u,int v)
{
    to[++cnt]=v;
    next[cnt]=first[u];
    first[u]=cnt;
    to[++cnt]=u;
    next[cnt]=first[v];
    first[v]=cnt;
}
int rank[MAXN],size[MAXN];
ll dp[MAXN];
void rank_dfs(int x,int fa)
{
    size[x]=1;
    dp[x]=rank[x];
    for(int i=first[x];i;i=next[i])
    {
        if(to[i]==fa)continue;
        rank[x]=rank[to[i]]+1;
        rank_dfs(to[i],x);
        size[x]+=size[to[i]];
    }
}
void dfs(int x,int fa)
{
    for(int i=first[x];i;i=next[i])
    {
        if(to[i]==fa)continue;
        dp[to[i]]=dp[x]+n-2*size[to[i]];
        dfs(to[i],x);
    }
}
int main()
{
    scanf("%d",&n);
    for(int i=1;i<n;i++){scanf("%d%d",&a,&b);add(a,b);}
    rank_dfs(1,0);
    dfs(1,0);
    int ans=1;
    for(int i=1;i<=n;i++)
        if(dp[i]>dp[ans])ans=i;
    cout<<ans;
    return 0;
}