// CSparse/Source/cs_pinv: construct an inverse permutation
// CSparse, Copyright (c) 2006-2022, Timothy A. Davis. All Rights Reserved.
// SPDX-License-Identifier: LGPL-2.1+
#include "cs.h"
/* pinv = p', or p = pinv' */
csi *cs_pinv (csi const *p, csi n)
{
    csi k, *pinv ;
    if (!p) return (NULL) ;                     /* p = NULL denotes identity */
    pinv = cs_malloc (n, sizeof (csi)) ;        /* 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 */
}