求最长路

#include<cstdio>
#include<iostream>
#include<queue>
using namespace std;
queue <int> t;
const int M=100001;
const int N=20001;
int summ,n,m;
double dis[N],w[M];
int vis[M],u[M],v[M],nx[M];
void add(int x,int y,double z)
{
	nx[++summ]=u[x];
	v[summ]=y;
	w[summ]=1-z;
	u[x]=summ;
}
void spfa(int s)
{
	for(int i=1;i<=m;i++)
	{
		dis[i]=-1;
		vis[i]=0;
	}
	t.push(s);
	dis[s]=1;
	vis[s]=1;
	while(!t.empty())
	{
		int tt=t.front();
		t.pop();
		vis[tt]=0;
		for(int i=u[tt];i;i=nx[i])
		{
			int vv=v[i];
			if(dis[vv]<dis[tt]*w[i])
			{
				dis[vv]=dis[tt]*w[i];
				if(!vis[i])
				{
					vis[i]=1;
					t.push(vv);
				}
			}
		}
	}
}
int main()
{
	int x,y,z;
	scanf("%d %d",&n,&m);
	for(int i=1;i<=n;i++)
	{
		scanf("%d %d %d",&x,&y,&z);
		add(x,y,(double)z/100.0);
		add(y,x,(double)z/100.0);
	}
	scan0bf("%d %d",&x,&y);
	spfa(x);
	printf("%.8lf",100/1.0/dis[y]);
}