2019西安邀请赛 M.Travel bfs二分

https://nanti.jisuanke.com/t/A1837

#include<bits/stdc++.h>
using namespace std;
#define IO ios::sync_with_stdio(false)
#define ll long long
#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define pii pair<int,int>
#define all(n) (n).begin(),(n).end()
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define QAQ sort(co+1,co+1+n)
const int maxn=1e5+5;
struct node
{
	ll v;
	ll len;
};
struct nodee{
	ll u;
	ll cnt;	//剩余次数 
};
vector<node> g[maxn];
vector<nodee> vec;//二分用vec比较 
int vis[maxn];
ll n,m,c,d,e,u,v,len;
bool bfs(int mid){
	ll dd=mid*d;
	memset(vis,0,sizeof vis);
	queue<nodee> que;
	vis[1]=1;
	que.push({1,mid*e});
	while(!que.empty()){
		nodee a=que.front();
		que.pop();
		ll num=a.cnt;
		ll v=a.u;
		if(v==n)
			return true;
		for(int i=0;i<g[v].size();i++){
			node b=g[v][i];
			ll dis=b.len;
			ll u=b.v;
			if(!vis[u] && dis<=dd && num>0){
				vis[u]=1;
				que.push({u,num-1});
			}
		}
	}
	return false;
}
int main()
{
    
    cin>>n>>m;
    cin>>c>>d>>e;
    while(m--){
    	cin>>u>>v>>len;
    	g[u].pb({v,len});
    	g[v].pb({u,len});
    	
	}
	ll l=1,r=maxn,mid=0,ans=0;
	while(l<=r){
		mid=(l+r)>>1; 
		if(bfs(mid)){
			ans=mid;
			r=mid-1;
		}
		else
			l=mid+1;
	}
	cout<<ans*c<<endl;
    return 0;
}