heapsort.java

Java数据结构开发包

/*
  Copyright (c) 1999, 2000 Brown University, Providence, RI
  
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  copyright notice and this permission notice appear in supporting
  documentation, and that the name of Brown University not be used in
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  without specific, written prior permission.
  
  BROWN UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
  SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  FITNESS FOR ANY PARTICULAR PURPOSE.  IN NO EVENT SHALL BROWN
  UNIVERSITY BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
  DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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  PERFORMANCE OF THIS SOFTWARE.
*/

package jdsl.core.algo.sorts;

import jdsl.core.api.*;
import jdsl.core.ref.ArrayHeap;



/**
 * Performs a heap-sort in O(n log n) time, provided only that
 * the replaceElement(.) method of the Sequence works in O(1) time
 * (and thus the style of implementation of the Sequence is not relevant).
 * All of the Positions of the sequence are preserved, but their
 * elements are moved around.
 *
 * @author Benoit Hudson (bh)
 * @author Luca Vismara (lv)
 * @version JDSL 2.1.1 
 */
public class HeapSort implements SortObject {
  
  public void sort (Sequence s, Comparator c) {
    PriorityQueue pq = new ArrayHeap(c,s.size()+1,false);

    PositionIterator pi = s.positions();
    while (pi.hasNext()) {
      Object elt = pi.nextPosition().element();
      pq.insert(elt,elt);
    }

    pi.reset();
    while (!pq.isEmpty())
      s.replaceElement(pi.nextPosition(),pq.removeMin());
  }

}