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

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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 
     
      #define M 1015using 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 <