马的遍历（BFS

https://www.luogu.org/problemnew/show/P1443

模板BFS......

 #include<iostream>
 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<cmath>
 #include<string>
 #include<cmath>
 #include<set>
 #include<vector>
 #include<stack>
 #include<queue>
 #include<map>
 using namespace std;
 #define ll long long
 #define se second
 #define fi first
 const int INF= 0x3f3f3f3f;
 const int N=1e5+;

 int n,m,a,b;
 int dx[]={,,,,-,-,-,-},dy[]={,-,,-,,-,,-};
 int step[][];
 bool vis[][];

 struct note
 {
     int x,y;
     int s;
 }w,p;

 queue<note>q;

 void bfs(int ax,int ay)
 {
     w.x=ax; w.y=ay; w.s=;
     vis[w.x][w.y]=;
     step[w.x][w.y]=w.s;

     q.push(w);
     while( !q.empty())
     {
         p=q.front();
         q.pop();
         for(int i=;i<;i++)
         {
             w.x=p.x+dx[i];
             w.y=p.y+dy[i];
             if(w.x<=n&&w.x>=&&w.y<=m&&w.y>=&&vis[w.x][w.y]==)
             {
                 vis[w.x][w.y]=;
                 w.s=p.s+;
                 step[w.x][w.y]=w.s;
                 q.push(w);
             }
         }
     }
 }

 int main()
 {
     cin>>n>>m>>a>>b;
     memset(step,-,sizeof(step));
     bfs(a,b);
     for(int i=;i<=n;i++){
         for(int j=;j<=m;j++)
             printf("%-5d",step[i][j]);
         cout<<endl;
     }
 }