MLE10分，bfs求调

#include<cstdio>
#include<queue>
using namespace std;
int n,xx,yy,ans;
bool a[1005][1005],vis[1005][1005];
char c;
struct place{
    int x,y,t;
}b,f;
queue<place> q;
int main(){
    scanf("%d\n",&n);
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            c=getchar();
            a[i][j]=c-'0';
            a[i][j]=!a[i][j];
        }
        scanf("\n");
    }
    scanf("%d%d%d%d",&b.x,&b.y,&xx,&yy);
    b.t=0;
    q.push(b);
    while(3){
        a[q.front().x][q.front().y]=1;
        if(q.front().x==xx&&q.front().y==yy){
            ans=q.front().t;
            break;
        }
        if(a[q.front().x-1][q.front().y]==1){
            f.x=q.front().x-1;
            f.y=q.front().y;
            f.t=q.front().t+1;
            q.push(f);
        }
        if(a[q.front().x+1][q.front().y]==1){
            f.x=q.front().x+1;
            f.y=q.front().y;
            f.t=q.front().t+1;
            q.push(f);
        }
        if(a[q.front().x][q.front().y-1]==1){
            f.x=q.front().x;
            f.y=q.front().y-1;
            f.t=q.front().t+1;
            q.push(f);
        }
        if(a[q.front().x][q.front().y+1]==1){
            f.x=q.front().x;
            f.y=q.front().y+1;
            f.t=q.front().t+1;
            q.push(f);
        }
        q.pop();
    }
    printf("%d",ans);
}

p1746