Function Run Fun

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.

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.

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

1 1 12 2 210 4 650 50 50-1 7 18-1 -1 -1

w(1, 1, 1) = 2w(2, 2, 2) = 4w(10, 4, 6) = 523w(50, 50, 50) = 1048576w(-1, 7, 18) = 1

/*if a <= 0 or b <= 0 or c <= 0, then w(a, b, c) returns:  1if 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)数组开三维22就行 */#include
    
     #include 
     
      using namespace std;int num[22][22][22]; int w(int a,int b,int c){	if(a<=0||b<=0||c<=0)	  return 1;	if(a>20||b>20||c>20)	  return num[20][20][20]=w(20,20,20);	if(num[a][b][c]!=-1)	   return num[a][b][c];	if(a
      
       
        >a>>b>>c){    	if(a==-1&&b==-1&&c==-1)    	 break;    	cout<<"w("<
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