就能大大优化空间
```cpp
#include <bits/stdc++.h>
using namespace std;
const int N = 50 + 5 , Q = 1e3 + 5 ;
int n , m , qus , sx , sy ;
char mp[N][N] ;
int dx[Q] , dy[Q] , flag[N][N][Q] ;
struct node {
int x , y , num ;
};
queue <node> q ;
void bfs()
{
q.push({sx , sy , 0}) ;
while(! q.empty() )
{
node u = q.front() , v ;
if(u.num == qus) break ;
q.pop() ;
for(int i = 1 ; ; i ++)
{
v.num = u.num + 1 ;
v.x = u.x + dx[v.num] * i ;
v.y = u.y + dy[v.num] * i ;
if(v.x < 1 || v.x > n || v.y < 1 || v.y > m) break ;
if(mp[v.x][v.y] == 'X') break ;
if(flag[v.x][v.y][v.num] == 1) break ;
flag[v.x][v.y][v.num] = 1 ;
q.push({v.x , v.y , v.num}) ;
}
}
return ;
}
int main()
{
cin >> n >> m ;
for(int i = 1 ; i <= n ; i ++)
{
for(int j = 1 ; j <= m ; j ++)
{
cin >> mp[i][j] ;
if(mp[i][j] == '*') sx = i , sy = j ;
}
}
cin >> qus ;
string s ;
for(int i = 1 ; i <= qus ; i ++)
{
cin >> s ;
if(s == "NORTH") dx[i] = -1 , dy[i] = 0 ;
if(s == "SOUTH") dx[i] = 1 , dy[i] = 0 ;
if(s == "WEST") dx[i] = 0 , dy[i] = -1 ;
if(s == "EAST") dx[i] = 0 , dy[i] = 1 ;
}
bfs() ;
mp[sx][sy] = '.' ;
while(! q.empty() )
{
node u = q.front() ;
q.pop() ;
mp[u.x][u.y] = '*' ;
}
for(int i = 1 ; i <= n ; i ++) cout << mp[i] + 1 << endl ;
return 0;
}
```
by Dream__maker @ 2024-02-22 17:25:15
对比[优化前](https://www.luogu.com.cn/record/148004361)和[优化后](https://www.luogu.com.cn/record/148005792)
by Dream__maker @ 2024-02-22 17:26:56
不过我这个做法好像空间大，效率还低 QwQ
by Dream__maker @ 2024-02-22 17:30:19
@[Dream__maker](/user/718017) 感谢，遇到了一模一样的问题，解决了。
仔细想想，其实就是遍历的时候会重复，导致程序效率低下，内存爆了。
~~~~大家一定要应以为戒~~~~
by sll00 @ 2024-04-27 15:15:47
@[sll00](/user/1243869) 嗯加油，顺便壶关（doge
by Dream__maker @ 2024-04-27 15:16:52
@[Dream__maker](/user/718017) 当然
by sll00 @ 2024-04-27 15:42:32