Luogu P1576

Topic link: Minimum cost

The fee for transferring A to B is x1, and the fee for transferring B to C is x2, then the fee for transferring from A to C is x1 * x2;

	if(dis[to] < dis[now] * e[i].w)
            dis[to] = dis[now] * e[i].w;

code show as below

#include<iostream>
#include<cstdio>
#include<bits/stdc++.h>
using namespace std;
const int N = 101000;
const int maxn = 2018;
struct Node{
	int do;
	int to;
	double w;
}e[N<<1];
int head[maxn];
double dis[maxn];
int n, m, x, y, st, en, val, cnt;
bool vis[maxn];
void init()
{
	memset(head,-1,sizeof(head));
	memset(vis,0,sizeof(vis));
	cnt = 0;
}
void add(int u,int v,double val)
{
	e [cnt] .to = v;
	e [cnt] .ne = head [u];
	e[cnt].w = 1 - val; // remaining fee
	head[u] = cnt ++;
}
void SPFA()
{
	queue<int>q;
	q.push(st);
	memset(dis,0,sizeof(dis));
	vis [st] = 1;
	dis [st] = 1;
	while(!q.empty())
	{
		int now = q.front();
		q.pop();
		for(int i=head[now];~i;i=e[i].ne)
		{
			int to = e[i].to;
			if(dis[to] < dis[now] * e[i].w )  
			{
				dis[to] = dis[now] * e[i].w;
				if(!vis[to])
				{
					q.push(to);
					vis [to] = 1;
				}
			}
		}
		vis[now] = 0;
	}
}
intmain()
{
	scanf("%d%d",&n,&m);
	init();
	for(int i=1;i<=m;i++)
	{
		scanf("%d%d%d",&x,&y,&val);
		add(x,y,double(val)/100);
		add(y,x,double(val)/100);
	}
	scanf("%d%d",&st,&en);
	SPFA();
	double ans = 100/dis[en];
	printf("%.8lf\n",ans);
	return 0;
}

Note the initialization and double! ! !