/*
* Copyright (c) 1998-2011 Caucho Technology -- all rights reserved
*
* This file is part of Resin(R) Open Source
*
* Each copy or derived work must preserve the copyright notice and this
* notice unmodified.
*
* Resin Open Source is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* Resin Open Source is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
* of NON-INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with Resin Open Source; if not, write to the
* Free SoftwareFoundation, Inc.
* 59 Temple Place, Suite 330
* Boston, MA 02111-1307 USA
*
* @author Scott Ferguson
*/
package com.caucho.util;
import java.util.ArrayList;
abstract public class Sort {
abstract public boolean lessThan(Object a, Object b);
private void quicksort(ArrayList list, int head, int tail)
{
if (tail - head < 2)
return;
else if (tail - head == 2) {
Object va = list.get(head);
Object vb = list.get(head + 1);
if (lessThan(vb, va)) {
list.set(head, vb);
list.set(head + 1, va);
}
return;
}
int center = head + 1;
Object pivot = list.get(head);
for (int i = head + 1; i < tail; i++) {
Object value = list.get(i);
if (lessThan(value, pivot)) {
Object centerValue = list.get(center);
list.set(center, value);
list.set(i, centerValue);
center++;
}
}
if (center == tail) {
Object tailValue = list.get(tail - 1);
list.set(head, tailValue);
list.set(tail - 1, pivot);
quicksort(list, head, tail - 1);
} else {
quicksort(list, head, center);
quicksort(list, center, tail);
}
}
public void sort(ArrayList list)
{
quicksort(list, 0, list.size());
}
}