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// CSparse/Source/cs_post: postorder a forest
// CSparse, Copyright (c) 2006-2022, Timothy A. Davis. All Rights Reserved.
// SPDX-License-Identifier: LGPL-2.1+
#include "cs.h"
/* post order a forest */
csi *cs_post (const csi *parent, csi n)
{
csi j, k = 0, *post, *w, *head, *next, *stack ;
if (!parent) return (NULL) ; /* check inputs */
post = cs_malloc (n, sizeof (csi)) ; /* allocate result */
w = cs_malloc (3*n, sizeof (csi)) ; /* get workspace */
if (!w || !post) return (cs_idone (post, NULL, w, 0)) ;
head = w ; next = w + n ; stack = w + 2*n ;
for (j = 0 ; j < n ; j++) head [j] = -1 ; /* empty linked lists */
for (j = n-1 ; j >= 0 ; j--) /* traverse nodes in reverse order*/
{
if (parent [j] == -1) continue ; /* j is a root */
next [j] = head [parent [j]] ; /* add j to list of its parent */
head [parent [j]] = j ;
}
for (j = 0 ; j < n ; j++)
{
if (parent [j] != -1) continue ; /* skip j if it is not a root */
k = cs_tdfs (j, k, head, next, post, stack) ;
}
return (cs_idone (post, NULL, w, 1)) ; /* success; free w, return post */
}
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