应该是头文件，一本通好像不支持万能头文件
by Little_Lily @ 2021-05-11 08:53:51
你的程序中
```cpp
a[x][y] = a[x + 2][y + 1] = a[x + 2][y - 1] = a[x - 2][y + 1] = a[x - 2][y - 1] = 1;
```
其中 $x-2$ 可能造成数组越界导致运行错误
by Link_Space @ 2021-05-11 09:01:18
@[孙励岩](/user/359252) 我以前ybt都用的万能头，没有错啊
by ImposterAnYu @ 2021-05-11 09:08:37
@[Link_Space](/user/278481)
```cpp
#include<bits/stdc++.h>
using namespace std;
unsigned long long n,m,x,y,i,j,b[25][25];
bool a[25][25];
int main(){
cin >> n >> m >> x >> y;
x += 2;
y += 2;
n += 2;
m += 2;
a[x][y] = a[x + 2][y + 1] = a[x + 2][y - 1] = a[x - 2][y + 1] = a[x - 2][y - 1] = 1;
a[x + 1][y + 2] = a[x - 1][y + 2] = a[x + 1][y - 2] = a[x - 1][y - 2] = 1;
b[2][2] = 1;
for(i = 3; i <= n; i++){
if(a[i][2]) continue;
b[i][2] = b[i - 1][2];
}
for(i = 3; i <= m; i++){
if(a[2][i]) continue;
b[2][i] = b[2][i - 1];
}
for(i = 3; i <= n; i++){
for(j = 3; j <= m; j++){
if(a[i][j]) continue;
b[i][j] = b[i - 1][j] + b[i][j - 1];
}
}
cout<< b[n][m] ;
return 0;
}
```
改完过了，谢啦~
by ImposterAnYu @ 2021-05-11 09:11:44