#include<bits/stdc++.h>
using namespace std;
long long ch[25][25][25];
long long fun(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 fun(20,20,20);
	else if(a<b&&b<c)
	{
		if(ch[a][b][c]!=-1)return ch[a][b][c];
		ch[a][b][c]=fun(a,b,c-1)+fun(a,b-1,c-1)+fun(a,b-1,c);
		return ch[a][b][c];
	}
	else 
	{
		if(ch[a][b][c]!=-1)return ch[a][b][c];
		ch[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);
		return ch[a][b][c];
	}
}
int main()
{
	long long a,b,c,ans;
	memset(ch,-1,sizeof(ch));
	while(1)
	{
		scanf("%lld %lld %lld",&a,&b,&c);
		if(a==-1&&b==-1&&c==-1)return 0;
		printf("w(%lld, %lld, %lld) = %lld\n",a,b,c,fun(a,b,c));
	}
	return 0;
}

测试结果：全WA

我找不到错误啊！！！