```cpp
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll x,y,z;
ll memory[30][30][30];
ll res;
ll f(ll x,ll y,ll z)
{
if(memory[x][y][z])
return memory[x][y][z];
else
{
if(x<=0 or y<=0 or z<=0)
return memory[x][y][z]=1;
else if(x>20 or y>20 or z>20)
if(memory[20][20][20])
return memory[20][20][20];
else
return memory[20][20][20]=memory[x][y][z]=f(x,y,z);
else if(x<y and y<z)
return memory[x][y][z]=f(x,y,z-1)+f(x,y-1,z-1)+f(x,y-1,z);
else
return memory[x][y][z]=f(x-1,y,z)+f(x-1,y-1,z)+f(x-1,y,z-1)-f(x-1,y-1,z-1);
}
}
signed main()
{
while(~scanf("%lld %lld %lld",&x,&y,&z) and (x!=-1 and y!=-1 and z!=-1))
{
memset(memory,0,sizeof memory);
printf("w(%lld, %lld, %lld) = ",x,y,z);
if(x>20)
x=21;
if(y>20)
y=21;
if(z>20)
z=21;
res=f(x,y,z);
printf("%lld",res);
puts("");
}
return 0;
}
```
改了一个细节，不过无伤MLE大雅
by Rainsleep @ 2022-06-23 22:01:03
前面有小于0和大于20的不要加记忆化，会爆掉
by Technablode @ 2022-06-23 22:01:24
~~为什么要 memset 呢 虽然这或许无关紧要~~
by StarLbright40 @ 2022-06-23 22:25:03
@[Technablode](/user/575802) 我没看懂，您能解释一下什么意思吗
by Rainsleep @ 2022-06-23 22:36:26
@[Rainsheeep](/user/666796) 万一有一个-114514，-114514，-114514的数据，你引用当前位置的内存就爆掉了
by Technablode @ 2022-06-24 08:41:27
```cpp
return memory[20][20][20]=memory[x][y][z]=f(x,y,z);
```
这里memory[x][y][z]会爆
by qkqwork @ 2022-10-11 13:16:49