拓扑排序:绿豆蛙的归宿

题目链接:点击这里

#include<cstdio>
#include<iostream>
#include<cstring>
#include<queue>
#include<algorithm>
typedef long long ll;
typedef long double ld;
using namespace std;
const int maxn=1e5+5;
const int maxm=2e5+5;
ll in[maxn],head[maxn],num=0,ans=0,out[maxn];
double dp[maxn];
struct node{
    
    
	ll next,to,len;
}kkk[maxm];
void addedge(ll u,ll v,ll w){
    
    
	kkk[++num].next=head[u];
	kkk[num].to=v;
	kkk[num].len=w;
	head[u]=num;
}
int main()
{
    
    	
	int n,m;
	scanf("%d%d",&n,&m);
	for(ll i=0;i<m;++i){
    
    
		ll u,v,w;
		scanf("%lld%lld%lld",&u,&v,&w);
		addedge(v,u,w);
		++out[u],++in[u];
	}
	queue<ll>q;
	q.push(n);
	while(!q.empty()){
    
    
		ll u=q.front();q.pop();
		for(ll i=head[u];i;i=kkk[i].next){
    
    
			ll v=kkk[i].to;
			dp[v]+=(kkk[i].len+dp[u])/out[v];
			--in[v];
			if(!in[v]) q.push(v);
			//printf("%d %d\n",v,in[v]);
		}
	}
	printf("%.2f",dp[1]);
    return 0;
}