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The Apache PDFBox library is an open source Java tool for working with PDF documents.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (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.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.pdfbox.util;
import java.util.ArrayDeque;
import java.util.Comparator;
import java.util.Deque;
import java.util.List;
/**
* see http://de.wikipedia.org/wiki/Quicksort.
*
* @author Uwe Pachler
* @author Manuel Aristaran
*/
public final class QuickSort
{
private QuickSort()
{
}
private static final Comparator OBJCOMP = new Comparator()
{
@Override
public int compare(Comparable object1, Comparable object2)
{
return object1.compareTo(object2);
}
};
/**
* Sorts the given list using the given comparator.
*
* @param list list to be sorted
* @param cmp comparator used to compare the object swithin the list
*/
public static void sort(List list, Comparator cmp)
{
int size = list.size();
if (size < 2)
{
return;
}
quicksort(list, cmp);
}
/**
* Sorts the given list using compareTo as comparator.
*
* @param list list to be sorted
*/
public static void sort(List list)
{
sort(list, (Comparator) OBJCOMP);
}
private static void quicksort(List list, Comparator cmp)
{
Deque stack = new ArrayDeque();
stack.push(0);
stack.push(list.size());
while (!stack.isEmpty())
{
int right = stack.pop();
int left = stack.pop();
if (right - left < 2)
{
continue;
}
int p = left + ((right - left) / 2);
p = partition(list, cmp, p, left, right);
stack.push(p + 1);
stack.push(right);
stack.push(left);
stack.push(p);
}
}
private static int partition(List list, Comparator cmp, int p, int start, int end)
{
int l = start;
int h = end - 2;
T piv = list.get(p);
swap(list, p, end - 1);
while (l < h)
{
if (cmp.compare(list.get(l), piv) <= 0)
{
l++;
}
else if (cmp.compare(piv, list.get(h)) <= 0)
{
h--;
}
else
{
swap(list, l, h);
}
}
int idx = h;
if (cmp.compare(list.get(h), piv) < 0)
{
idx++;
}
swap(list, end - 1, idx);
return idx;
}
private static void swap(List list, int i, int j)
{
T tmp = list.get(i);
list.set(i, list.get(j));
list.set(j, tmp);
}
}