Thread: Permutation?

  1. #1
    Registered User
    Join Date
    Mar 2005
    Posts
    14

    Permutation?

    Code:
    #include <stdio.h>
    #include "Boolean.h"
    #include "combinatorics.h"
    #include <limits.h>
    
    /* For all the functions below, return TRUE if the
       calculation is successful, FALSE if overflow occurs
       Return the calculated value in the pass by reference
       parameter provided
    */
    
    Boolean calcFactorial (int n, int* nfact)
    {
        *nfact = 1;
    
    	while(n > 0)
    	{
    	       *nfact = *nfact * n;
    		   n--;		   
    	}
    	if(*nfact < 0x7fffffff)
    		   {
    		      return TRUE;	 
    		   }
    	       else
    		   {
    		      return FALSE;
    		   }      
    }
    
    /*
    Combination means C(n,r) = n!/( r! * (n-r)! ) 
    where C(n,r) is the number of r-element subsets of an n-element set.
    Better formula derived from above is:
              n ( n-1 ) ( n-2 ) ... ( n-r+1 ) 
     C(n,r) = ------------------------------- 
              r ( r-1 ) ( r-2 ) ... (3)(2)(1) 
    
    
      Return True if calculation is successful. False if
      Overflow occurs.
    */
    
    Boolean calcCNR( int n, int r, int* cnr )
    {
        #define min(n,r)  (((n) < (r)) ? (n) : (r));
    
        int multiplier = n;
        int divisor = 1;
        int k;
        INT_MAX;
    
        k = min(r, n - r);
        //printf("n=%d, r=%d, k=%d\n", n, r, k);
        
        
    	*cnr = 1;
        while (divisor <= k) 
    	{
    		if(INT_MAX / multiplier < *cnr) 
    		{ 
    			printf("Overflow detected\n");
    		    return FALSE;
    		}
    		else
    		{
            *cnr = ((*cnr * multiplier) / divisor);
       		
            //printf("Intermediate *cnr=%d\n", *cnr);
            multiplier--;
            divisor++;
    		}
        }
    	return TRUE;
    
    }
    Boolean calcPNR( int cnr, int rfact, int* pnr )
    {
    
    }
    here is my program so far for calculating factorials, combinations, and permutations. Can someone show me an algorithm or pseudocode to calculate the calcPNR(permuation) function please?

  2. #2
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    Kermi3

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