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 )
{

}

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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?

Please don't double post