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CSparseJ is a Java port of CSparse: a Concise Sparse matrix package.
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/*
 * CXSparse: a Concise Sparse matrix package.
 * Copyright (C) 2006-2011, Timothy A. Davis.
 * Copyright (C) 2011-2012, Richard W. Lincoln.
 * http://www.cise.ufl.edu/research/sparse/CXSparse
 *
 * -------------------------------------------------------------------------
 *
 * CXSparseJ 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.
 *
 * CXSparseJ 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
 *
 */

package edu.emory.mathcs.csparsej.tdcomplex ;

/**
 * Depth-first-search of a tree.
 *
 * @author Piotr Wendykier ([email protected])
 * @author Richard Lincoln ([email protected])
 *
 */
public class DZcs_tdfs {

	/**
	 * Depth-first search and postorder of a tree rooted at node j
	 *
	 * @param j
	 *            postorder of a tree rooted at node j
	 * @param k
	 *            number of nodes ordered so far
	 * @param head
	 *            head[i] is first child of node i; -1 on output
	 * @param head_offset
	 *            the index of the first element in array head
	 * @param next
	 *            next[i] is next sibling of i or -1 if none
	 * @param next_offset
	 *            the index of the first element in array next
	 * @param post
	 *            postordering
	 * @param post_offset
	 *            the index of the first element in array post
	 * @param stack
	 *            size n, work array
	 * @param stack_offset
	 *            the index of the first element in array stack
	 * @return new value of k, -1 on error
	 */
	public static int cs_tdfs(int j, int k, int[] head, int head_offset, int[] next, int next_offset,
		int[] post, int post_offset, int[] stack, int stack_offset)
	{
		int i, p, top = 0 ;
		if (head == null || next == null || post == null || stack == null)
			return (-1) ;					/* check inputs */
		stack [stack_offset + 0] = j ;				/* place j on the stack */
		while (top >= 0)					/* while (stack is not empty) */
		{
			p = stack [stack_offset + top] ;		/* p = top of stack */
			i = head [head_offset + p] ;			/* i = youngest child of p */
			if (i == -1)
			{
				top-- ;					/* p has no unordered children left */
				post [post_offset + (k++)] = p ;	/* node p is the kth postordered node */
			}
			else
			{
				head [head_offset + p] = next [next_offset + i] ;  /* remove i from children of p */
				stack [stack_offset + (++top)] = i ;	/* start dfs on child node i */
			}
		}
		return (k) ;
	}

}