AC代码
```cpp
#include<bits/stdc++.h>
using namespace std;
long long f[30][30][30];
long long w(long long a,long long b,long long c)
{
if (a<=0||b<=0||c<=0)
return 1;
else if (a>20||b>20||c>20)
return w(20,20,20);
else if (f[a][b][c]>0)
return f[a][b][c];
else if (a<b&&b<c)
return f[a][b][c]=w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);
else
return f[a][b][c]=w(a-1,b,c)+w(a-1,b-1,c)+w(a-1,b,c-1)-w(a-1,b-1,c-1);
}
int main()
{
long long a,b,c;
while (1)
{
cin>>a>>b>>c;
if (a==-1&&b==-1&&c==-1)
return 0;
cout<<"w("<<a<<", "<<b<<", "<<c<<") = "<<w(a,b,c)<<endl;
}
return 0;
}
```
w函数内顺序错了，因为:
$$这种时候我们就按最上面的条件来算$$
by MvemiY @ 2022-06-30 19:37:31
@[lizhehao2009](/user/727871) 就是递归的时候爆了
by MvemiY @ 2022-06-30 19:38:12
@[Birdly](/user/620253) 感谢您的帮助！
by lizhehao2009 @ 2022-06-30 19:38:36