先上代码 乖巧的记忆化搜索

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
long long f[25][25][25];
long long fun(long long a,long long b,long long c)
{
	if(f[a][b][c]!=-1)
	return f[a][b][c];
	else
	 {
		if(a<=0||b<=0||c<=0)
    	return 1;
		else if(a>20||b>20||c>20)
		return f[a][b][c]=fun(20,20,20);
		else if(a<b&&b<c)
		return f[a][b][c]=fun(a,b,c-1)+fun(a,b-1,c-1)-fun(a,b-1,c);
		else
		return f[a][b][c]=fun(a-1,b,c)+fun(a-1,b-1,c)+fun(a-1,b,c-1)-fun(a-1,b-1,c-1);
	}

}
int main()
{
	long long a,b,c;
	memset(f,-1,sizeof(f));
	while(a!=-1||b!=-1||c!=-1)
	{
		cin>>a>>b>>c;
        if(a<0||b<0||c<0) cout<<"w("<<a<<","<<b<<","<<c<<")="<<fun(0,0,0)<<endl;
        else if(a>20||b>20||c>20) cout<<"w("<<a<<","<<b<<","<<c<<")="<<fun(21,21,21)<<endl;
		else
		cout<<"w("<<a<<","<<b<<","<<c<<")="<<fun(a,b,c)<<endl;
		if(a==-1&&b==-1&&c==-1)
		break;
	
	}
	return 0;
 } 

自己测了一遍答案都是对的，但是就是全WA，不知道是不是输入输出的问题