[POI2008]Sta

两遍DFS……

第一遍维护自己儿子到自己的

第二遍维护自己祖先到自己的

用了内嵌汇编……

//Lib
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<ctime>
 
#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<queue>
//#include<stack>
#include<set>
#include<map>
using namespace std;
//Macro
#define rep(i,a,b)  for(int i=a,tt=b;i<=tt;++i)
#define drep(i,a,b) for(int i=a,tt=b;i>=tt;--i)
#define erep(i,e,x) for(int i=x;i;i=e[i].next)
#define irep(i,x)   for(__typeof(x.begin()) i=x.begin();i!=x.end();i++)
#define read()  (strtol(ipos,&ipos,10))
#define sqr(x)  ((x)*(x))
#define pb  push_back
#define PS  system("pause");
typedef long long   ll;
typedef pair<int,int> pii;
const int oo=~0U>>1;
const double inf=1e100;
const double eps=1e-6;
string name="", in=".in", out=".out";
//Var
struct E
{
    int node,next;
}e[2000008];
struct N
{
    long long up,down,size; 
}node[1000008];
int stack[20000000],bak;
char file[20000000],*ipos;
int h[1000008],n,tot;
void add(int a,int b){e[++tot].next=h[a];e[tot].node=b;h[a]=tot;}
void DFS1(int fa,int u)
{
    erep(i,e,h[u])
    {
        if(e[i].node!=fa)
        {
            DFS1(u,e[i].node);
            node[u].size+=node[e[i].node].size;
            node[u].down+=node[e[i].node].down;
        }
    }
    node[u].down+=node[u].size;
    node[u].size++;
}
void DFS2(int fa,int u)
{
    if(u!=1)node[u].up=node[fa].up+n-node[u].size+node[fa].down-(node[u].size+node[u].down);
    erep(i,e,h[u])
        if(e[i].node!=fa)DFS2(u,e[i].node); 
}
void CallDFS(void (*p)(int,int))
{
    __asm__ __volatile__
    (
        "mov %%esp,%0\n"
        "mov %1,%%esp\n"
        :"=g"(bak)
        :"g"(stack+20000000-1)
        :
    );
    (*p)(0,1);
    __asm__ __volatile__
    (
        "mov %0,%%esp\n"
        :
        :"g"(bak)
        :
    );  
}
void Work()
{
    fread(ipos=file,20000000,1,stdin);
    n=read();int a,b;
    rep(i,1,n-1)
    {
        a=read();b=read();
        add(a,b),add(b,a);
    }
    void (*p)(int,int)=DFS1;
    CallDFS(p);
    p=DFS2;
    CallDFS(p);
    int pos=1;
    rep(i,1,n)if(node[i].up+node[i].down>node[pos].up+node[pos].down)pos=i;
    cout<<pos<<endl;    
}
int main()
{
//  freopen((name+in).c_str(),"r",stdin);
//  freopen((name+out).c_str(),"w",stdout);
//  Init();
    Work();
    return 0;
}