Function Run Fun-递归+细节处理

We all love recursion! Don't we?

Consider a three-parameter recursive function w(a, b, c):

if a <= 0 or b <= 0 or c <= 0, then w(a, b, c) returns: 
1

if a > 20 or b > 20 or c > 20, then w(a, b, c) returns: 
w(20, 20, 20)

if a < b and b < c, then w(a, b, c) returns: 
w(a, b, c-1) + w(a, b-1, c-1) - w(a, b-1, c)

otherwise it returns: 
w(a-1, b, c) + w(a-1, b-1, c) + w(a-1, b, c-1) - w(a-1, b-1, c-1)

This is an easy function to implement. The problem is, if implemented directly, for moderate values of a, b and c (for example, a = 15, b = 15, c = 15), the program takes hours to run because of the massive recursion.

Input

The input for your program will be a series of integer triples, one per line, until the end-of-file flag of -1 -1 -1. Using the above technique, you are to calculate w(a, b, c) efficiently and print the result.

Output

Print the value for w(a,b,c) for each triple.

Sample Input

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

Sample Output

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

 #include<stdio.h>
 #include<iostream>
 #include<string.h>
 #define inf 0x3f3f3f3f
 typedef long long ll;
 using namespace std;

 int book[][][];
 int w(int a,int b,int c)
 {
     if(a<=||b<=||c<=)
        return ;
     else if(a>||b>||c>)
         return w(,,);
     else if(book[a][b][c]!=-)
         return book[a][b][c];
     else if(a<b&&b<c)
         return book[a][b][c]=w(a,b,c-)+w(a,b-,c-)-w(a,b-,c);
     else
         return book[a][b][c]=w(a-,b,c)+w(a-,b-,c)+w(a-,b,c-)-w(a-,b-,c-);
   //  return book[a][b][c];
 }
 int main()
 {
     int a,b,c;
     while(~scanf("%d %d %d",&a,&b,&c))
     {
         if(a==-&&b==-&&c==-)
             break;
         memset(book,-,sizeof(book));
         printf("w(%d, %d, %d) = %d\n",a,b,c,w(a,b,c));
     }
     return ;
 }

int w(int a,int b,int c)
{
    if(a>=&&a<=&&b>=&&b<=&&c>=&&c<=&&book[a][b][c]!=-)//防止越界
        return book[a][b][c];
    if(a<=||b<=||c<=)
        return ;
    else if(a>||b>||c>)
        return w(,,);
    else if(a<b&&b<c)
        return book[a][b][c]=w(a,b,c-)+w(a,b-,c-)-w(a,b-,c);
    else
        return book[a][b][c]=w(a-,b,c)+w(a-,b-,c)+w(a-,b,c-)-w(a-,b-,c-);
}