pjs/grendel/calypso/util/QSort.java

109 строки
3.3 KiB
Java
Исходник Обычный вид История

1998-09-09 04:52:38 +04:00
/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil -*-
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.0 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
* the License for the specific language governing rights and limitations
* under the License.
*
* The Original Code is the Grendel mail/news client.
*
* The Initial Developer of the Original Code is Netscape Communications
* Corporation. Portions created by Netscape are Copyright (C) 1997
* Netscape Communications Corporation. All Rights Reserved.
*/
package calypso.util;
/** Implements QuickSort, on an array of objects.
An implementor of `Comparer' is passed in to compare two objects.
*/
public class QSort {
private Comparer comp;
/** Create a QSort object.
One way to use this would with dynamic class creation:
<PRE>
QSort sorter = new QSort(new Comparer() {
public int compare(Object a, Object b) {
if (a.key == b.key) return 0;
else if (a.key < b.key) return -1;
else return 1;
}
});
sorter.sort(array);
</PRE>
*/
public QSort(Comparer c) {
comp = c;
}
/** Sorts the array, according to the Comparer. */
public void sort(Object[] list) {
quicksort(list, 0, list.length - 1);
}
/** Sorts a subsequence of the array, according to the Comparer. */
public void sort(Object[] list, int start, int end) {
quicksort(list, start, end - 1);
}
private void quicksort(Object[] list, int p, int r) {
if (p < r) {
int q = partition(list,p,r);
if (q == r) {
q--;
}
quicksort(list,p,q);
quicksort(list,q+1,r);
}
}
private int partition (Object[] list, int p, int r) {
Object pivot = list[p];
int lo = p;
int hi = r;
while (true) {
while (comp.compare(list[hi], pivot) >= 0 &&
lo < hi) {
hi--;
}
while (comp.compare(list[lo], pivot) < 0 &&
lo < hi) {
lo++;
}
if (lo < hi) {
Object T = list[lo];
list[lo] = list[hi];
list[hi] = T;
}
else return hi;
}
}
// public static void main(String argv[]) {
// String array[] = { "7", "3", "0", "4", "5", "6", "2", "1" };
// QSort sorter = new QSort(new Comparer() {
// public int compare(Object a, Object b) {
// int ai = Integer.parseInt((String) a);
// int bi = Integer.parseInt((String) b);
// if (ai == bi) return 0;
// else if (ai < bi) return -1;
// else return 1;
// }
// });
// sorter.sort(array);
// for (int i = 0; i < array.length; i++)
// System.out.print(array[i] + " ");
// System.out.println();
// }
}