2057The Lost House

大神的指导，加上大神的题解文档，我自己照着他的代码打了一遍，通过了

详细看看网站http://blog.sina.com.cn/s/blog_5f5353cc0100hd08.html

我的ACCEPT代码，想通了就感觉个之前做过的一道聚会的树形dp有点像

#include "iostream"
#include "algorithm"
#include "string.h"
#include <iomanip>
#define M 1015
using namespace std;
int tree[M][M],leave[M],success[M],fail[M];
char h[M];

int cmp(int u,int v) {
      return (fail[u]+2)*leave[v]<(fail[v]+2)*leave[u];
}

void work(int a){
  int i,j,tem[M];
  if(tree[a][0]==0){
    leave[a]=1;
    success[a]=0;
    fail[a]=0;
  }
  for(i=1;i<=tree[a][0];i++){
    work(tree[a][i]);
  }
  for(i=1;i<=tree[a][0];i++){
    if(h[a]=='N')fail[a]+=fail[tree[a][i]]+2;
    leave[a]+=leave[tree[a][i]];
  }
  for(i=1;i<=tree[a][0];i++){
    tem[i]=tree[a][i];
  }
  sort(tem+1,tem+tree[a][0]+1,cmp);
  for(i=1,j=0;i<=tree[a][0];i++){
    success[a]+=(j+1)*leave[tem[i]]+success[tem[i]];
    j+=fail[tem[i]]+2;
  }
}

int main(){
  char b;
  int a,n,i;
  while(cin>>n&&n){
    memset(tree,0,sizeof(tree));
    memset(success,0,sizeof(success));
    memset(fail,0,sizeof(fail));
    memset(leave,0,sizeof(leave));
    for(i=1;i<=n;i++){
      cin>>a>>b;
      if(a!=-1){
        tree[a][0]++;
        tree[a][tree[a][0]]=i;
      }
      h[i]=b;
    }
    work(1);
    double tem=(double)success[1]/(double)leave[1];
    cout <<setiosflags(ios::fixed);
    cout<< setprecision(4)<<tem<<endl;
  }
}