P1443 马的遍历
本蒟蒻的代码：

#include<iostream>
using namespace std;
int n,m,x,y;
struct node{
    int x;
    int y;
}q[160001];
int leftt=1,rightt=1;
int vis[401][401]={},map_step[401][401];
int dx[8] = {-1,1,-1,1,2,2,-2,-2};
int dy[8] = {-2,-2,2,2,-1,1,1,-1};
void bfs(){
    q[rightt].x = x;
    q[rightt].y = y;
    vis[x][y]=1;
    map_step[x][y] = 0;
    while(leftt<=rightt){
        int tx,ty;
        for(int i=0;i<8;i++){
            tx = q[leftt].x + dx[i];
            ty = q[leftt].y + dy[i];
            if(tx>n || tx<1 || ty>m|| ty<1 || vis[tx][ty]==1)continue;
            ++rightt;
            q[rightt].x = tx;
            q[rightt].y = ty;
            vis[tx][ty] = 1;
            map_step[tx][ty] = map_step[ q[leftt].x ][ q[leftt].y ] + 1;

        }
        ++leftt;
    }
    return;
}
int main(){
    cin>>n>>m>>x>>y;
    for(int i=1;i<=n;++i){
        for(int j=1;j<=m;++j){
            map_step[i][j]=-1;
            vis[i][j]=0;
        }
    }
    bfs();
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(map_step[i][j]==-1){
                cout<<"-1   ";
            }else{
                cout<<map_step[i][j]<<"    ";
            }
        }
        cout<<endl;
    }
    return 0;
} 
/*
输入只有一行四个整数，分别为 n, m, x, y。
0    3    2    
3    -1   1    
2    1    4    
*/