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Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright notice, this
9 * list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
23 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#pragma once
28
29#include <AK/StdLibExtras.h>
30
31namespace AK {
32
33template<typename T>
34bool is_less_than(const T& a, const T& b)
35{
36 return a < b;
37}
38
39template<typename Iterator, typename LessThan>
40void quick_sort(Iterator start, Iterator end, LessThan less_than = is_less_than)
41{
42 int size = end - start;
43 if (size <= 1)
44 return;
45
46 int pivot_point = size / 2;
47 auto pivot = *(start + pivot_point);
48
49 if (pivot_point)
50 swap(*(start + pivot_point), *start);
51
52 int i = 1;
53 for (int j = 1; j < size; ++j) {
54 if (less_than(*(start + j), pivot)) {
55 swap(*(start + j), *(start + i));
56 ++i;
57 }
58 }
59
60 swap(*start, *(start + i - 1));
61 quick_sort(start, start + i - 1, less_than);
62 quick_sort(start + i, end, less_than);
63}
64
65}
66
67using AK::quick_sort;