#include "cs.h" /* return a random permutation vector, the identity perm, or p = n-1:-1:0. * seed = -1 means p = n-1:-1:0. seed = 0 means p = identity. otherwise * p = random permutation. */ int *cs_randperm (int n, int seed) { int *p, k, j, t ; if (seed == 0) return (NULL) ; /* return p = NULL (identity) */ p = cs_malloc (n, sizeof (int)) ; /* allocate result */ if (!p) return (NULL) ; /* out of memory */ for (k = 0 ; k < n ; k++) p [k] = n-k-1 ; if (seed == -1) return (p) ; /* return reverse permutation */ srand (seed) ; /* get new random number seed */ for (k = 0 ; k < n ; k++) { j = k + (rand ( ) % (n-k)) ; /* j = rand int in range k to n-1 */ t = p [j] ; /* swap p[k] and p[j] */ p [j] = p [k] ; p [k] = t ; } return (p) ; }