学过最短路的都能做。

#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#include<algorithm>
using namespace std;
const int NR=40001;
vector<int> g[NR];
bool f[NR];
int n,dis1[NR],dis2[NR],dis3[NR];
void spfa1()
{
	queue<int> q;
	q.push(1);
	memset(dis1,0x3f,sizeof(dis1));
	dis1[1]=0;
	f[1]=true;
	while(!q.empty())
	{
		int u=q.front(),i;
		q.pop();
		f[u]=false;
		for(i=0;i<g[u].size();i++)
			if(dis1[u]+1<dis1[g[u][i]])
			{
				dis1[g[u][i]]=dis1[u]+1;
				if(!f[g[u][i]])
				{
					q.push(g[u][i]);
					f[g[u][i]]=true;
				}
			}
	}
	return; 
}
void spfa2()
{
	queue<int> q;
	q.push(2);
	memset(dis2,0x3f,sizeof(dis2));
	dis2[2]=0;
	memset(f,false,sizeof(f)); 
	f[2]=true;
	while(!q.empty())
	{
		int u=q.front(),i;
		q.pop();
		f[u]=false;
		for(i=0;i<g[u].size();i++)
			if(dis2[u]+1<dis2[g[u][i]])
			{
				dis2[g[u][i]]=dis2[u]+1;
				if(!f[g[u][i]])
				{
					q.push(g[u][i]);
					f[g[u][i]]=true;
				}
			}
	}
	return; 
}
void spfa3()
{
	queue<int> q;
	q.push(n);
	memset(dis3,0x3f,sizeof(dis3));
	dis3[n]=0;
	memset(f,false,sizeof(f));
	f[n]=true;
	while(!q.empty())
	{
		int u=q.front(),i;
		q.pop();
		f[u]=false;
		for(i=0;i<g[u].size();i++)
			if(dis3[u]+1<dis3[g[u][i]])
			{
				dis3[g[u][i]]=dis3[u]+1;
				if(!f[g[u][i]])
				{
					q.push(g[u][i]);
					f[g[u][i]]=true;
				}
			}
	}
	return; 
}
int main()
{
	int b,e,p,m,i;
	cin>>b>>e>>p>>n>>m;
	while(m--)
	{
		int u,v;
		cin>>u>>v;
		g[u].push_back(v);
		g[v].push_back(u);
	}
	spfa1();
	spfa2();
	spfa3();
	long long ans=1ll*b*dis1[n]+1ll*e*dis2[n];
	for(i=1;i<=n;i++) ans=min(ans,1ll*b*dis1[i]+1ll*e*dis2[i]+1ll*p*dis3[i]);
	cout<<ans;
	return 0;
}