绿豆蛙的归宿

#include<cstdio>
#include<iostream>
#include<cstring>
#include<queue>
#define mem(a,b) memset(a,b,sizeof(a))
#define dd double
using namespace std;
int read()
{
    int ans=0;char q=getchar();
    while(q<'0'||q>'9')q=getchar();
    while(q>='0'&&q<='9'){ans=ans*10+q-'0';q=getchar();}
    return ans;
}
const int N=100010;
struct son
{
    int v,next,w;
};
son a1[N<<1];
int first[N<<1],e;

void addbian(int u,int v,int w)
{
    a1[e].w=w;
    a1[e].v=v;
    a1[e].next=first[u];
    first[u]=e++;
}

int n,m;
int u,o,p;
double indegree[N],outdegree[N];
int tuo[N],now;
double f[N];
double ans;
double gai[N];
queue<int> q;

void qiutuo()
{
    tuo[++now]=1;
    q.push(1);
    while(!q.empty())
    {
        int k=q.front();
        q.pop();
        for(int i=first[k];i!=-1;i=a1[i].next)
        {
            int temp=a1[i].v;
            --indegree[temp];
            if(!indegree[temp])
            {
                tuo[++now]=temp;
                q.push(temp);
            }
        }
    }
}

void out11()
{
    printf("
");
    for(int i=1;i<=n;++i)
      printf("%d ",tuo[i]);
    printf("
");
    for(int i=1;i<=n;++i)
      printf("%.0lf ",indegree[i]);
    printf("
");
    for(int i=1;i<=n;++i)
      printf("%.0lf ",outdegree[i]);
    printf("
");
    for(int i=1;i<=n;++i)
      printf("%.2lf ",f[i]);
    printf("
");
}

int main(){
    //freopen("1.txt","r",stdin);
    freopen("ldfrog.in","r",stdin);
    freopen("ldfrog.out","w",stdout);
    mem(first,-1);
    n=read();m=read();
    for(int i=1;i<=m;++i)
    {
        u=read();o=read();p=read();
        ++indegree[o];
        ++outdegree[u];
        addbian(u,o,p);
    }
    
    for(int i=1;i<n;++i)
        gai[i]=(dd)1/outdegree[i];
    
    qiutuo();
    f[1]=1;
    for(int i=1;i<=n;++i)
        for(int j=first[tuo[i]];j!=-1;j=a1[j].next)
        {
            int temp=a1[j].v;
            f[temp]+=f[tuo[i]]*gai[tuo[i]];
        }
    
    for(int i=1;i<=n;++i)
        for(int j=first[i];j!=-1;j=a1[j].next)
            ans+=(f[i]*gai[i]*(dd)a1[j].w);
            
    printf("%.2lf",ans);
    
    //out11();
    
//    while(1);
    return 0;
}