bzoj 3036: 绿豆蛙的归宿

23333sb题都做不对，，，感觉傻傻哒。。。23333333333333，一开始简直是直接真·乱搞啊。。

#include <bits/stdc++.h>
#define LL long long
#define lowbit(x) x&(-x)
#define inf 0x3f3f3f3f
using namespace std;
inline int ra()
{
    int x=0,f=1; char ch=getchar();
    while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();}
    while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
int n,cnt,m;
int head[100005],d[100005],in[100005];
double f[100005];
bool vis[100005];
struct edge{
    int to,next,v;
}e[200005];
void insert(int x, int y, int v)
{
    e[++cnt].next=head[x]; e[cnt].to=y; e[cnt].v=v; head[x]=cnt; d[x]++; 
}
void dfs(int x)
{
    if (!vis[x]) vis[x]=1; else return;
    for (int i=head[x];i;i=e[i].next)
    {
        dfs(e[i].to);
        f[x]+=(double)(f[e[i].to]+e[i].v)/(double)d[x];
    }
}
int main(int argc, char const *argv[])
{
    n=ra(); m=ra();
    for (int i=1; i<=m; i++) 
    {
        int x=ra(),y=ra(),v=ra();
        insert(x,y,v);
    }
    dfs(1);    
    printf("%.2lf
",f[1]);
    return 0;
}