/* -*- 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:
      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);
      
*/ 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(); // } }