1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// <algorithm>
10
11// template<BidirectionalIterator Iter>
12// requires ShuffleIterator<Iter>
13// && LessThanComparable<Iter::value_type>
14// constexpr bool // constexpr in C++20
15// next_permutation(Iter first, Iter last);
16
17#include <algorithm>
18#include <cassert>
19
20#include "test_macros.h"
21#include "test_iterators.h"
22
23#include <cstdio>
24
25TEST_CONSTEXPR_CXX14 int factorial(int x)
26{
27 int r = 1;
28 for (; x; --x)
29 r *= x;
30 return r;
31}
32
33template <class Iter>
34TEST_CONSTEXPR_CXX20 bool
35test()
36{
37 int ia[] = {1, 2, 3, 4, 5, 6};
38 const int sa = sizeof(ia)/sizeof(ia[0]);
39 int prev[sa];
40 for (int e = 0; e <= sa; ++e)
41 {
42 int count = 0;
43 bool x;
44 do
45 {
46 std::copy(ia, ia+e, prev);
47 x = std::next_permutation(Iter(ia), Iter(ia+e));
48 if (e > 1)
49 {
50 if (x)
51 assert(std::lexicographical_compare(prev, prev+e, ia, ia+e));
52 else
53 assert(std::lexicographical_compare(ia, ia+e, prev, prev+e));
54 }
55 ++count;
56 } while (x);
57 assert(count == factorial(e));
58 }
59 return true;
60}
61
62int main(int, char**)
63{
64 test<bidirectional_iterator<int*> >();
65 test<random_access_iterator<int*> >();
66 test<int*>();
67
68#if TEST_STD_VER >= 20
69 static_assert(test<bidirectional_iterator<int*>>());
70 static_assert(test<random_access_iterator<int*>>());
71 static_assert(test<int*>());
72#endif
73
74 return 0;
75}
76

source code of libcxx/test/std/algorithms/alg.sorting/alg.permutation.generators/next_permutation.pass.cpp