import java.util.Comparator;

/**
 * AStarComparator - A comparator for HSearchNodes which bases
 * comparison on f(n), the estimated cost to reach node a goal node
 * through node n.
 *
 * @author Todd Neller
 * @version 1.0
 *

Copyright (C) 2004 Todd Neller

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program 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 General Public License for more details.

Information about the GNU General Public License is available online at:
  http://www.gnu.org/licenses/
To receive a copy of the GNU General Public License, write to the Free
Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.

 */

public class AStarComparator implements Comparator<HSearchNode> {

    /**
     * <code>compare</code> - compare two nodes, returning a value
     * indicating their ordering according to f(n), the estimated cost
     * to reach node a goal node * through node n.  If f(n1) < f(n2),
     * -1 is returned.  If f(n1) = f(n2), 0 is returned.  If f(n1) >
     * f(n2), 1 is returned.
     *
     * @param n1 a <code>HSearchNode</code> value - the first node of
     * the comparison
     * @param n2 a <code>HSearchNode</code> value - the second node of
     * the comparison
     * @return a <code>int</code> value - -1 if f(n1) < f(n2); 0 if
     * f(n1) = f(n2); 1 if f(n1) > f(n2) */
    public int compare(HSearchNode n1, HSearchNode n2) 
    {
	double f1 = n1.getF();
	double f2 = n2.getF();
	if (f1 < f2)
	    return -1;
	else if (f1 == f2)
	    return 0;
	else
	    return 1;
    }    
	
}