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1   package cz.cuni.amis.utils.astar;
2   
3   import java.util.Comparator;
4   import java.util.Map;
5   
6   /**
7    * This comparator is a tricky object - it serves for the {@link AStarHeap} to compare nodes inside the heap.
8    * <p><p>
9    * The trick is, that it is initialized {@link AStarHeapComparator#AStarHeapComparator(Map)} with a map
10   * that contains node's costs that are used during the comparation inside {@link AStarHeapComparator#compare(Object, Object)}.
11   * No magic yet, ha? Well, the magic is that this map is not cloned... simply a pointer to this very instance passed
12   * inside the constructor is saved to you may alter the cost as you wish to! Which is truly needed by the {@link AStar} class
13   * that is obtaining nodes' costs from the {@link AStarMap} implementor.
14   * 
15   * @author Jimmy
16   *
17   * @param <NODE>
18   */
19  public class AStarHeapComparator<NODE> implements Comparator {
20  	
21  	private Map<NODE, Integer> values;
22  	
23  	public AStarHeapComparator(Map<NODE, Integer> estimatedCosts){
24  		values = estimatedCosts;
25  	}
26  
27  	public int compare(Object arg0, Object arg1) {
28  		return values.get(arg0).intValue() - values.get(arg1).intValue();
29  	}
30  
31  }