TYVJP1933 绿豆蛙的归宿

 1 #include<algorithm>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<iostream>
 5 #include<vector>
 6 #include<queue>
 7 using namespace std;
 8 const int mxn=120000;
 9 vector<int>e[mxn];
10 vector<int>len[mxn];
11 queue<int>q;
12 int out[mxn],deg[mxn]; 
13 double f[mxn];
14 int n,m;
15 
16 int main(){
17     cin>>n>>m;
18     int i,j;
19     int a,b,c;
20     for(i=1;i<=m;i++){
21         scanf("%d %d %d",&a,&b,&c);
22         e[b].push_back(a);//入边 
23         len[b].push_back(c);//边长 
24         out[a]++;
25     }
26     for(i=1;i<=n;i++)deg[i]=out[i];//备份 
27     q.push(n);
28     while(!q.empty()){
29         int v=q.front(),u,le;
30         q.pop();
31         for(i=0;i<e[v].size();i++){
32             u=e[v][i];le=len[v][i];
33             f[u]+=(f[v]+le)/out[u];
34             deg[u]--;
35             if(!deg[u]) q.push(u);
36         }
37     }
38     printf("%.2lf",f[1]);
39     return 0;
40 }