[Help-gsl] help with permutations

[Nathan Moore]

Hello,

I'm working on a program which needs all possible permutations of a set of N
keys (N is obviously a small number).  I cobbled together some code
(attached) this morning, but I'm guessing there's a more efficient way to
get all possible permutations of the "keys" (they are indicies to a number
of different arrays)

Any thoughts would be appreciated!

Nathan Moore

Source follows:


#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <gsl/gsl_permutation.h>

int
main()
{

       int             j, i, N = 10;
       int             keys[N];

       gsl_permutation *s = gsl_permutation_alloc(N);
       gsl_permutation_init(s);

       for (j = 0; j < 5; j++) {

               printf("permutation: ");
               gsl_permutation_fprintf(stdout, s, " %u ");
               printf("\n");

               for (i = 0; i < N; i++) {
                       keys[i] = gsl_permutation_get(s, i);
               }

               printf("keys:        ");
               for (i = 0; i < N; i++) {
                       printf(" %d ", keys[i]);
               }
               printf("\n\n");

/* at this point I need to do a bunch of work with the keys, which are
indicies
 to several other arrays */

               gsl_permutation_next(s);
       }

       printf("\n");
       return 1;
}