RE一个点......

1000*1000的那个点总是RE，求查错 QAQ

#include<bits/stdc++.h>
using namespace std;
int p[1051][1051],n,x,y,fx,fy;
int xg[4]={0,0,1,-1};
int yg[4]={1,-1,0,0};
struct queue_s{
    int x,y;
    int s;
}que_s[1150001];
void bfs(){
    int head=0,tail=1,i;
    que_s[1].x=x;que_s[1].y=y;que_s[1].s=0;
    while(head<=tail){
        head++;
        while(que_s[head].x==0||que_s[head].y==0){
            head++;
            if(head>tail) return ; 
        }
        int h1=que_s[head].x,h2=que_s[head].y;
        for(i=0;i<4;i++){
            int jd1=h1+xg[i],jd2=h2+yg[i];
            if(!p[jd1][jd2]&&jd1>0&&jd2>0&&jd1<=n&&jd2<=n){
                p[jd1][jd2]=1;
                tail++;
                que_s[tail].x=jd1;
                que_s[tail].y=jd2;
                que_s[tail].s=que_s[head].s+1;
                if(jd1==fx&&jd2==fy){
                    cout<<que_s[tail].s;
                    head=INT_MAX;tail=0;
                }
            }
        }
    }
}
int main(){
    cin>>n;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            scanf("%1d",&p[i][j]);
    cin>>x>>y>>fx>>fy;
    p[x][y]=1;
    bfs();
    return 0;
}