马的遍历 | 正确题解

#include<bits/stdc++.h>
using namespace std;
int dx[8] = {-2,-1,1,2,2,1,-1,-2};
int dy[8] = {-1,-2,-2,-1,1,2,2,1};
struct stu{
int x,y,step;
}r,l;
bool vis[1010][1010];
int a[1010][1010];
int n,m,sx,sy;
queue<stu> q;
void bfs(){
q.push({sx,sy,0});
vis[sx][sy] = 1;
while(q.size()){
r = q.front();
q.pop();
a[r.x][r.y] = r.step;
for(int i = 0;i < 8;i++){
l.x = r.x + dx[i];
l.y = r.y + dy[i];
if(1 <= l.x && l.x <= n && 1 <= l.y && l.y <= m && vis[l.x][l.y] == 0){
l.step = r.step + 1;
vis[l.x][l.y] = 1;
q.push(l);
}
}
}
}
int main(){
cin>>n>>m>>sx>>sy;
for(int i = 1;i <= n;i++){
for(int j = 1;j <= m;j++){
a[i][j] = -1;
}
}
bfs();
for(int i = 1;i <= n;i++){
for(int j = 1;j <= m;j++){
cout<<a[i][j]<<" ";
}
cout<<endl;
}
return 0;
}