cs_pinv.c

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#include "cs.h"
/* pinv = p', or p = pinv' */
int *cs_pinv (int const *p, int n)
{
    int k, *pinv ;
    if (!p) return (NULL) ;                     /* p = NULL denotes identity */
    pinv = cs_malloc (n, sizeof (int)) ;        /* allocate result */
    if (!pinv) return (NULL) ;                  /* out of memory */
    for (k = 0 ; k < n ; k++) pinv [p [k]] = k ;/* invert the permutation */
    return (pinv) ;                             /* return result */
}