2488 绿豆蛙的归宿

#include<stack>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define N 10000
using namespace std;
stack<double>q;
int n,m,x,y,z,tot;
double p[N],ans;
int in[N],out[N],head[N];
struct Edge
{
    int from,to,dis,next;
    double gl;
} edge[N<<2];
void add(int x,int y,int z)
{
    tot++;
    edge[tot].to=y;
    edge[tot].dis=z;
    edge[tot].next=head[x];
    head[x]=tot;
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1; i<=m; i++)
        {
            scanf("%d%d%d",&x,&y,&z);
            add(x,y,z);
            in[y]++;
            out[x]++;
        }
    p[1]=1;
    q.push(1);
    int now;
    while(!q.empty())
        {
            now=q.top();
            q.pop();
            for(int i=head[now]; i; i=edge[i].next)
                {
                    p[edge[i].to]+=p[now]*1.0/out[now];
                    edge[i].gl=p[now]*1.0/out[now];
                    in[edge[i].to]--;
                    if(!in[edge[i].to]) q.push(edge[i].to);
                }
        }
    for(int i=1;i<=m;i++) ans+=edge[i].gl*edge[i].dis;
    printf("%.2lf",ans);
    return 0;
}