01: /*
02: * Copyright (c) 1998-2008 Caucho Technology -- all rights reserved
03: *
04: * This file is part of Resin(R) Open Source
05: *
06: * Each copy or derived work must preserve the copyright notice and this
07: * notice unmodified.
08: *
09: * Resin Open Source is free software; you can redistribute it and/or modify
10: * it under the terms of the GNU General Public License as published by
11: * the Free Software Foundation; either version 2 of the License, or
12: * (at your option) any later version.
13: *
14: * Resin Open Source is distributed in the hope that it will be useful,
15: * but WITHOUT ANY WARRANTY; without even the implied warranty of
16: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17: * of NON-INFRINGEMENT. See the GNU General Public License for more
18: * details.
19: *
20: * You should have received a copy of the GNU General Public License
21: * along with Resin Open Source; if not, write to the
22: * Free SoftwareFoundation, Inc.
23: * 59 Temple Place, Suite 330
24: * Boston, MA 02111-1307 USA
25: *
26: * @author Scott Ferguson
27: */
28:
29: package com.caucho.util;
30:
31: import java.util.ArrayList;
32:
33: abstract public class Sort {
34: abstract public boolean lessThan(Object a, Object b);
35:
36: private void quicksort(ArrayList list, int head, int tail) {
37: if (tail - head < 2)
38: return;
39: else if (tail - head == 2) {
40: Object va = list.get(head);
41: Object vb = list.get(head + 1);
42:
43: if (lessThan(vb, va)) {
44: list.set(head, vb);
45: list.set(head + 1, va);
46: }
47:
48: return;
49: }
50:
51: int center = head + 1;
52: Object pivot = list.get(head);
53: for (int i = head + 1; i < tail; i++) {
54: Object value = list.get(i);
55:
56: if (lessThan(value, pivot)) {
57: Object centerValue = list.get(center);
58: list.set(center, value);
59: list.set(i, centerValue);
60: center++;
61: }
62: }
63:
64: if (center == tail) {
65: Object tailValue = list.get(tail - 1);
66: list.set(head, tailValue);
67: list.set(tail - 1, pivot);
68:
69: quicksort(list, head, tail - 1);
70: } else {
71: quicksort(list, head, center);
72: quicksort(list, center, tail);
73: }
74: }
75:
76: public void sort(ArrayList list) {
77: quicksort(list, 0, list.size());
78: }
79: }
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