开了快读WA了九个点

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
#include<cstring>
#include<cctype>
#define oo (1ll<<31)-1
using namespace std;
inline void read(int &x)
{
	x=0;char ch=getchar();
	while(ch<'0'||ch>'9')ch=getchar();
	while(ch>'0'&&ch<'9')
	{
		x=(x<<3)+(x<<1)+(ch^'0');
		ch=getchar();
	}
}
struct node
{
	int dis;
	int to;
	int next;
}edge[21111];
int dis[10000];
int head[10000];
int v[10000];
int tot=0;
priority_queue<pair<int,int> >q;
void add(int x,int y,int w)
{
	edge[++tot].dis=w;
	edge[tot].to=y;
	edge[tot].next=head[x];
	head[x]=tot; 
}
int main()
{
	int n,m,a,b;
	read(n);read(m);read(a);read(b);
	for(int i=1;i<=m;i++)
	{
		int x,y,w;
		read(x);read(y);read(w);
		add(x,y,w);
		add(y,x,w);
	}
	for(int i=1;i<=n;i++)
	{
		dis[i]=oo;
	}
	memset(v,0,sizeof(v)); 
	dis[a]=0;
	q.push(make_pair(0,a));
	while(!q.empty())
	{
		int i=q.top().second;q.pop();
		if(v[i])continue;
		v[i]=1;	
		for(int j=head[i];j;j=edge[j].next)
		{
			int k=edge[j].to;
			if(dis[k]>dis[i]+edge[j].dis)
			{
	//			cout<<"point:"<<x<<"  ";
	//			cout<<to<<":"<<dis[to];
				dis[k]=dis[i]+edge[j].dis;
				q.push(make_pair(-dis[k],k));
	//			cout<<"-->"<<dis[to]<<endl;
			}
		}
	}
	cout<<dis[b]<<endl;
	return 0;
}