dijkstra不到哪里错了

#include<bits/stdc++.h>                                                                               
using namespace std;
struct node
{
	int to,nxt;
	double val;
}a[114514*2];
int n,m,cnt,head[114514],x[114514],y[114514];
double dist[114514];
bool vis[114514];
priority_queue<pair<double,int> >q;
double f(int x1,int yy,int x2,int y2)
{
	return sqrt(abs(x1-x2)*abs(x1-x2)+abs(yy-y2)*abs(yy-y2));
}
void add(int u,int v,int w)
{
	a[++cnt].to=v;
	a[cnt].val=w;
	a[cnt].nxt=head[u];
	head[u]=cnt;
}
void djs(int s)
{
	memset(vis,0,sizeof vis);
	memset(dist,0x3f,sizeof dist);
	dist[s]=0;
	q.push(make_pair(0,s));
	while(!q.empty())
	{
		int x=q.top().second;
		q.pop();
		if(vis[x])
			continue;
		vis[x]=1;
		for(int i=head[x];i;i=a[i].nxt)
		{
			int y=a[i].to;
			if(dist[y]>dist[x]+a[i].val)
			{
				dist[y]=dist[x]+a[i].val;
				q.push(make_pair(-dist[y],y));
			}
		}
	}
}
int s,t;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>x[i]>>y[i];
	cin>>m;
	for(int i=1;i<=m;i++)
	{
		int u,v;
		cin>>u>>v;
    	add(u,v,f(x[u],y[u],x[v],y[v]));
		add(v,u,f(x[u],y[u],x[v],y[v]));
	}
	cin>>s>>t;
	djs(s);
	printf("%.2lf",dist[t]);
}