/*
 * CXSPARSE: a Concise Sparse Matrix package - Extended.
 * Copyright (c) 2006-2009, Timothy A. Davis.
 * http://www.cise.ufl.edu/research/sparse/CXSparse
 * 
 * CXSparse is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * CXSparse is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this Module; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "cs.h"
/* post order a forest */
CS_INT *cs_post (const CS_INT *parent, CS_INT n)
{
    CS_INT j, k = 0, *post, *w, *head, *next, *stack ;
    if (!parent) return (NULL) ;                        /* check inputs */
    post = cs_malloc (n, sizeof (CS_INT)) ;                /* allocate result */
    w = cs_malloc (3*n, sizeof (CS_INT)) ;                 /* 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 */
}