BZOJ 1131: [POI2008]Sta

/**************************************************************
    Problem: 1131
    User: BeiYu
    Language: C++
    Result: Accepted
    Time:8028 ms
    Memory:78700 kb
****************************************************************/
 
#include <cstdio>
#include <vector>
#include <iostream>
using namespace std;
 
typedef long long LL;
const int N = 1000005;
 
int n;
int s[N],d[N];
LL sd[N];
LL ans1,ans2;
int nxt[N<<1],gto[N<<1],e,h[N];
 
inline int in(int x=0,char ch=getchar()){ while(ch>‘9‘ || ch<‘0‘) ch=getchar();
    while(ch>=‘0‘ && ch<=‘9‘) x=x*10+ch-‘0‘,ch=getchar();return x; }
 
void Add_Edge(int fr,int to){ nxt[++e]=h[fr],gto[e]=to,h[fr]=e; }
 
void DFS1(int u=1,int fa=0) {
    s[u]=1,sd[u]=d[u]=d[fa]+1;
    for(int i=h[u],v;i;i=nxt[i]) if((v=gto[i])!=fa) {
        DFS1(v,u),s[u]+=s[v],sd[u]+=sd[v];
    }
}
void DFS2(int u=1,int fa=1,LL x=0) {
    LL res=x+(sd[u]-(LL)d[u]*s[u]);
//  cout<<u<<" "<<res<<endl;
    if(ans2<res || (ans2==res && ans1>u)) ans1=u,ans2=res;
    for(int i=h[u],v;i;i=nxt[i]) if((v=gto[i])!=fa) {
        DFS2(v,u,x+n-s[v]+(sd[u]-sd[v])-(LL)d[u]*(s[u]-s[v]));  
    }
}
 
int main(){
//  freopen("in.in","r",stdin);
     
    n=in();
    for(int i=1,u,v;i<n;i++) u=in(),v=in(),Add_Edge(u,v),Add_Edge(v,u);
     
    d[0]=-1;
    DFS1();
    ans1=1,ans2=sd[1];
    DFS2();
    cout<<ans1<<endl;
     
    return 0;
}