20pts求助

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=100010;
int n,m;
struct d{
	long double x,y;
}dot[N];
int head[N];
struct p{
	int nxt,to;long double data;
}edge[N];
int cnt;
void add(int u,int v,long double w)
{
	edge[++cnt].to=v;
	edge[cnt].data=w;
	edge[cnt].nxt=head[u];
	head[u]=cnt;
}
long double dis[N];
int vis[N];
int s,t;
void spfa()
{
	//memset(dis,0x3f,sizeof dis);
	for (int i=1;i<=n+10;i++)dis[i]=10000000000.0;
	queue<int>q;
	vis[s]=1;dis[s]=0;
	q.push(s);
	while(!q.empty())
	{
		int u=q.front();q.pop();
		vis[u]=0;
		for (int i=head[u];i;i=edge[i].nxt)
		{//cout<<1;
			int v=edge[i].to;long double w=edge[i].data;
		//	cout<<dis[v]<<endl;
			if (dis[v]>dis[u]+w)
			{//cout<<1;
				dis[v]=dis[u]+w;//cout<<dis[v]<<endl;
				if (vis[v]==0)q.push(v),vis[v]=1;
			}
		}
	}
}
signed main()
{
	cin>>n;
	for (int i=1;i<=n;i++)
	{
		cin>>dot[i].x>>dot[i].y;
	}
	cin>>m;
	for (int i=1;i<=n;i++)
	{
		int a,b;
		cin>>a>>b;
		long double xa=dot[a].x,xb=dot[b].x,ya=dot[a].y,yb=dot[b].y;
		long double j=sqrt((xa-xb)*(xa-xb)+(ya-yb)*(ya-yb));
		add(a,b,j);add(b,a,j); 
	}
	cin>>s>>t;
	spfa();
	printf("%.2Lf",dis[t]);
	return 0;
}