## 题目答案！
```
#include<bits/stdc++.h>
using namespace std;
long long h[50][50][50];
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(h[a][b][c]!=0)return h[a][b][c];
else if(a<b&&b<c)
h[a][b][c]=w(a,b,c-1)+w(a,b-1,c-1)-w(a,b-1,c);// here
else
h[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);
return h[a][b][c];
}
int main(){
long long a,b,c;
while(cin>>a>>b>>c){
if(a==-1&&b==-1&&c==-1)
break;
cout<<"w("<< a <<", "<< b <<", "<< c << ") = ";
cout<<w(a, b, c)<<endl;
}
return 0;
}
```
by C_ccx_N @ 2023-06-28 20:50:08
@[C_ccx_N](/user/1025456) tlqtj
by zwyyy @ 2023-06-28 21:44:14