jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2020, the SerenityOS developers.
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 */
6
7#include <LibTest/TestCase.h>
8
9#include <AK/Noncopyable.h>
10#include <AK/QuickSort.h>
11#include <AK/StdLibExtras.h>
12
13TEST_CASE(sorts_without_copy)
14{
15 struct NoCopy {
16 AK_MAKE_NONCOPYABLE(NoCopy);
17
18 public:
19 NoCopy() = default;
20 NoCopy(NoCopy&&) = default;
21
22 NoCopy& operator=(NoCopy&&) = default;
23
24 int value { 0 };
25 };
26
27 Array<NoCopy, 64> array;
28
29 // Test the dual pivot quick sort.
30 for (size_t i = 0; i < 64; ++i)
31 array[i].value = (64 - i) % 32 + 32;
32
33 dual_pivot_quick_sort(array, 0, array.size() - 1, [](auto& a, auto& b) { return a.value < b.value; });
34
35 for (size_t i = 0; i < 63; ++i)
36 EXPECT(array[i].value <= array[i + 1].value);
37
38 // Test the single pivot quick sort.
39 for (size_t i = 0; i < 64; ++i)
40 array[i].value = (64 - i) % 32 + 32;
41
42 AK::single_pivot_quick_sort(array.begin(), array.end(), [](auto& a, auto& b) { return a.value < b.value; });
43
44 for (size_t i = 0; i < 63; ++i)
45 EXPECT(array[i].value <= array[i + 1].value);
46}
47
48// This test case may fail to construct a worst-case input if the pivot choice
49// of the underlying quick_sort no longer matches the one used here.
50// So it provides no strong guarantees about the properties of quick_sort.
51TEST_CASE(maximum_stack_depth)
52{
53 int const size = 256;
54 int* data = new int[size];
55
56 for (int i = 0; i < size; i++) {
57 data[i] = i;
58 }
59
60 // Construct the data in such a way that the assumed pivot choice
61 // of (size / 2) causes the partitions to be of worst case size.
62 for (int i = 0; i < size / 2; i++) {
63 swap(data[i], data[i + (size - i) / 2]);
64 }
65
66 // Measure the depth of the call stack through the less_than argument
67 // of quick_sort as it gets copied for each recursive call.
68 struct DepthMeasurer {
69 int& max_depth;
70 int depth { 0 };
71 DepthMeasurer(int& max_depth)
72 : max_depth(max_depth)
73 {
74 }
75 DepthMeasurer(DepthMeasurer const& obj)
76 : max_depth(obj.max_depth)
77 {
78 depth = obj.depth + 1;
79 if (depth > max_depth) {
80 max_depth = depth;
81 }
82 }
83 bool operator()(int& a, int& b)
84 {
85 return a < b;
86 }
87 };
88
89 int max_depth = 0;
90 DepthMeasurer measurer(max_depth);
91 AK::single_pivot_quick_sort(data, data + size, measurer);
92
93 EXPECT(max_depth <= 64);
94
95 for (int i = 0; i < size; i++)
96 EXPECT(data[i] == i);
97
98 delete[] data;
99}