POJ- 1579 Function Run Fun

1 1 1
2 2 2
10 4 6
50 50 50
-1 7 18
-1 -1 -1

w(1, 1, 1) = 2
w(2, 2, 2) = 4
w(10, 4, 6) = 523
w(50, 50, 50) = 1048576
w(-1, 7, 18) = 1
//这是非常简单的记忆化搜索入门题
/*
Source Code
Problem: 1579		User: 2486
Memory: 432K		Time: 0MS
Language: G++		Result: Accepted

*/
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn=20+5;
int dp[maxn][maxn][maxn];
int a,b,c;
int dfs(int x,int y,int z){
    if(x<=0||y<=0||z<=0)return 1;
    else if(x<=20&&y<=20&&z<=20&&dp[x][y][z]!=-1)return dp[x][y][z];
    else if(x>20||y>20||z>20)return dfs(20,20,20);
    else if(x<y&&y<z)return dp[x][y][z]=dfs(x,y,z-1)+dfs(x,y-1,z-1)-dfs(x,y-1,z);
    else return dp[x][y][z]=dfs(x-1,y,z)+dfs(x-1,y-1,z)+dfs(x-1,y,z-1)-dfs(x-1,y-1,z-1);
}
int main()
{
    memset(dp,-1,sizeof(dp));
    while(~scanf("%d%d%d",&a,&b,&c),a!=-1||b!=-1||c!=-1){
        printf("w(%d, %d, %d) = %d\n",a,b,c,dfs(a,b,c));
    }
    return 0;
}