求助

// luogu-judger-enable-o2
#include<bits/stdc++.h>
using namespace std;
int ans[1001][1001];
int ax[1001][1001],n,m;
int dx[8]= {2,-2,2,-2,-1,1,-1,1};
int dy[8]= {1,1,-1,-1,2,2,-2,-2};
int head,tail,x,y;
struct px {
    int x;
    int y;
    int step;
} a[10001];
void bfs(int stax,int stay) {
    head=0;
    tail=1;
    a[1].x=stax;
    a[1].y=stay;
    a[1].step=1;
    while(head<=tail) {
        ++head;
        x=a[head].x;
        y=a[head].y;
        for(int i=0; i<8; i++) {
            int nx=x+dx[i];
            int ny=y+dy[i];
            if(nx>=1&&nx<=n&&ny>=1&&ny<=m) {
                if(ax[nx][ny]==0) {
                    ax[nx][ny]=1;
                    ++tail;
                    a[tail].x=nx;
                    a[tail].y=ny;
                    a[tail].step=a[head].step+1;
                    ans[nx][ny]=a[tail].step-1;
                }
            }
        }
    }
}
int main() {
    int a1,b1,l=-1,l1=0;
    cin>>n>>m>>a1>>b1;
    bfs(a1,b1);
    for(int i=1; i<=n; i++) {
        for(int j=1; j<=m; j++) {
            if(i==a1&&j==b1) 
                printf("%-5d",l1);
            else if(((n==1||m==1)||(n==2||m==2))&&((i==a1+1&&j==b1)||(i==a1-1&&j==b1)||(i==a1&&j==b1+1)||(i==a1&&j==b1-1)))
            printf("%-5d",l);
            else if(ans[i][j]==0)
            printf("%-5d",l);
            else
                printf("%-5d",ans[i][j]);
        }
        cout<<endl;
    }
    return 0;
}