[alg.sort]

# 26 Algorithms library [[algorithms]](./#algorithms)

## 26.8 Sorting and related operations [[alg.sorting]](alg.sorting#alg.sort)

### 26.8.2 Sorting [alg.sort]

#### [26.8.2.1](#sort) sort [[sort]](sort)

[🔗](#lib:sort)

`template<class RandomAccessIterator>
  constexpr void sort(RandomAccessIterator first, RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator>
  void sort(ExecutionPolicy&& exec,
            RandomAccessIterator first, RandomAccessIterator last);

template<class RandomAccessIterator, class Compare>
  constexpr void sort(RandomAccessIterator first, RandomAccessIterator last,
                      Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
  void sort(ExecutionPolicy&& exec,
            RandomAccessIterator first, RandomAccessIterator last,
            Compare comp);

template<[random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Comp = ranges::less,
         class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I, Comp, Proj>
  constexpr I
    ranges::sort(I first, S last, Comp comp = {}, Proj proj = {});
template<[random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]") R, class Comp = ranges::less, class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R>, Comp, Proj>
  constexpr borrowed_iterator_t<R>
    ranges::sort(R&& r, Comp comp = {}, Proj proj = {});

template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<I> S,
         class Comp = ranges::less, class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I, Comp, Proj>
  I ranges::sort(Ep&& exec, I first, S last, Comp comp = {}, Proj proj = {});
template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R, class Comp = ranges::less,
         class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R>, Comp, Proj>
  borrowed_iterator_t<R> ranges::sort(Ep&& exec, R&& r, Comp comp = {}, Proj proj = {});
`

[1](#sort-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8795)

Let comp be less{} and proj be identity{} for the overloads with no parameters by those names[.](#sort-1.sentence-1)

[2](#sort-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8800)

*Preconditions*: For the overloads in namespace std,RandomAccessIterator meets
the [*Cpp17ValueSwappable*](swappable.requirements#:Cpp17ValueSwappable "16.4.4.3 Swappable requirements [swappable.requirements]") requirements ([[swappable.requirements]](swappable.requirements "16.4.4.3 Swappable requirements")) and
the type of *first meets
the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [31](utility.arg.requirements#tab:cpp17.moveconstructible "Table 31: Cpp17MoveConstructible requirements")) and[*Cpp17MoveAssignable*](utility.arg.requirements#:Cpp17MoveAssignable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [33](utility.arg.requirements#tab:cpp17.moveassignable "Table 33: Cpp17MoveAssignable requirements")) requirements[.](#sort-2.sentence-1)

[3](#sort-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8809)

*Effects*: Sorts the elements in the range [first, last)
with respect to comp and proj[.](#sort-3.sentence-1)

[4](#sort-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8814)

*Returns*: last for the overloads in namespace ranges[.](#sort-4.sentence-1)

[5](#sort-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8818)

*Complexity*: Let N be last - first[.](#sort-5.sentence-1)

O(NlogN) comparisons and projections[.](#sort-5.sentence-2)

#### [26.8.2.2](#stable.sort) stable_sort [[stable.sort]](stable.sort)

[🔗](#lib:stable_sort)

`template<class RandomAccessIterator>
  constexpr void stable_sort(RandomAccessIterator first, RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator>
  void stable_sort(ExecutionPolicy&& exec,
                   RandomAccessIterator first, RandomAccessIterator last);

template<class RandomAccessIterator, class Compare>
  constexpr void stable_sort(RandomAccessIterator first, RandomAccessIterator last,
                             Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
  void stable_sort(ExecutionPolicy&& exec,
                   RandomAccessIterator first, RandomAccessIterator last,
                   Compare comp);

template<[random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Comp = ranges::less,
         class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I, Comp, Proj>
  constexpr I ranges::stable_sort(I first, S last, Comp comp = {}, Proj proj = {});
template<[random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]") R, class Comp = ranges::less, class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R>, Comp, Proj>
  constexpr borrowed_iterator_t<R>
    ranges::stable_sort(R&& r, Comp comp = {}, Proj proj = {});

template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<I> S,
         class Comp = ranges::less, class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I, Comp, Proj>
  I ranges::stable_sort(Ep&& exec, I first, S last, Comp comp = {}, Proj proj = {});
template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R, class Comp = ranges::less,
         class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R>, Comp, Proj>
  borrowed_iterator_t<R>
    ranges::stable_sort(Ep&& exec, R&& r, Comp comp = {}, Proj proj = {});
`

[1](#stable.sort-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8863)

Let comp be less{} and proj be identity{} for the overloads with no parameters by those names[.](#stable.sort-1.sentence-1)

[2](#stable.sort-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8868)

*Preconditions*: For the overloads in namespace std,RandomAccessIterator meets
the [*Cpp17ValueSwappable*](swappable.requirements#:Cpp17ValueSwappable "16.4.4.3 Swappable requirements [swappable.requirements]") requirements ([[swappable.requirements]](swappable.requirements "16.4.4.3 Swappable requirements")) and
the type of *first meets
the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [31](utility.arg.requirements#tab:cpp17.moveconstructible "Table 31: Cpp17MoveConstructible requirements")) and[*Cpp17MoveAssignable*](utility.arg.requirements#:Cpp17MoveAssignable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [33](utility.arg.requirements#tab:cpp17.moveassignable "Table 33: Cpp17MoveAssignable requirements")) requirements[.](#stable.sort-2.sentence-1)

[3](#stable.sort-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8877)

*Effects*: Sorts the elements in the range [first, last)
with respect to comp and proj[.](#stable.sort-3.sentence-1)

[4](#stable.sort-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8882)

*Returns*: last for the overloads in namespace ranges[.](#stable.sort-4.sentence-1)

[5](#stable.sort-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8886)

*Complexity*: Let N be last - first[.](#stable.sort-5.sentence-1)

If enough extra memory is available, Nlog(N) comparisons[.](#stable.sort-5.sentence-2)

Otherwise, at most Nlog2(N) comparisons[.](#stable.sort-5.sentence-3)

In either case, twice as many projections as the number of comparisons[.](#stable.sort-5.sentence-4)

[6](#stable.sort-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8893)

*Remarks*: Stable ([[algorithm.stable]](algorithm.stable "16.4.6.8 Requirements for stable algorithms"))[.](#stable.sort-6.sentence-1)

#### [26.8.2.3](#partial.sort) partial_sort [[partial.sort]](partial.sort)

[🔗](#lib:partial_sort)

`template<class RandomAccessIterator>
  constexpr void partial_sort(RandomAccessIterator first,
                              RandomAccessIterator middle,
                              RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator>
  void partial_sort(ExecutionPolicy&& exec,
                    RandomAccessIterator first,
                    RandomAccessIterator middle,
                    RandomAccessIterator last);

template<class RandomAccessIterator, class Compare>
  constexpr void partial_sort(RandomAccessIterator first,
                              RandomAccessIterator middle,
                              RandomAccessIterator last,
                              Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
  void partial_sort(ExecutionPolicy&& exec,
                    RandomAccessIterator first,
                    RandomAccessIterator middle,
                    RandomAccessIterator last,
                    Compare comp);

template<[random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Comp = ranges::less,
         class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I, Comp, Proj>
  constexpr I
    ranges::partial_sort(I first, I middle, S last, Comp comp = {}, Proj proj = {});
template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<I> S,
         class Comp = ranges::less, class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I, Comp, Proj>
  I ranges::partial_sort(Ep&& exec, I first, I middle, S last, Comp comp = {}, Proj proj = {});
`

[1](#partial.sort-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8936)

Let comp be less{} and proj be identity{} for the overloads with no parameters by those names[.](#partial.sort-1.sentence-1)

[2](#partial.sort-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8941)

*Preconditions*: [first, middle) and [middle, last) are valid ranges[.](#partial.sort-2.sentence-1)

For the overloads in namespace std,RandomAccessIterator meets
the [*Cpp17ValueSwappable*](swappable.requirements#:Cpp17ValueSwappable "16.4.4.3 Swappable requirements [swappable.requirements]") requirements ([[swappable.requirements]](swappable.requirements "16.4.4.3 Swappable requirements")) and
the type of *first meets
the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [31](utility.arg.requirements#tab:cpp17.moveconstructible "Table 31: Cpp17MoveConstructible requirements")) and[*Cpp17MoveAssignable*](utility.arg.requirements#:Cpp17MoveAssignable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [33](utility.arg.requirements#tab:cpp17.moveassignable "Table 33: Cpp17MoveAssignable requirements")) requirements[.](#partial.sort-2.sentence-2)

[3](#partial.sort-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8951)

*Effects*: Places the first middle - first elements
from the range [first, last)
as sorted with respect to comp and proj into the range [first, middle)[.](#partial.sort-3.sentence-1)

The rest of the elements in the range [middle, last)
are placed in an unspecified order[.](#partial.sort-3.sentence-2)

[4](#partial.sort-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8961)

*Returns*: last for the overload in namespace ranges[.](#partial.sort-4.sentence-1)

[5](#partial.sort-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8965)

*Complexity*: Approximately (last - first) * log(middle - first) comparisons, and
twice as many projections[.](#partial.sort-5.sentence-1)

[🔗](#partial.sort-itemdecl:2)

`template<[random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]") R, class Comp = ranges::less, class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R>, Comp, Proj>
  constexpr borrowed_iterator_t<R>
    ranges::partial_sort(R&& r, iterator_t<R> middle, Comp comp = {}, Proj proj = {});
`

[6](#partial.sort-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8979)

*Effects*: Equivalent to:return ranges::partial_sort(ranges::begin(r), middle, ranges::end(r), comp, proj);

[🔗](#partial.sort-itemdecl:3)

`template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R,
         class Comp = ranges::less, class Proj = identity>
  requires [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R>, Comp, Proj>
  borrowed_iterator_t<R>
    ranges::partial_sort(Ep&& exec, R&& r, iterator_t<R> middle, Comp comp = {},
                         Proj proj = {});
`

[7](#partial.sort-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8997)

*Effects*: Equivalent to:return ranges::partial_sort(std::forward<Ep>(exec), ranges::begin(r), middle,
 ranges::end(r), comp, proj);

#### [26.8.2.4](#partial.sort.copy) partial_sort_copy [[partial.sort.copy]](partial.sort.copy)

[🔗](#lib:partial_sort_copy)

`template<class InputIterator, class RandomAccessIterator>
  constexpr RandomAccessIterator
    partial_sort_copy(InputIterator first, InputIterator last,
                      RandomAccessIterator result_first,
                      RandomAccessIterator result_last);
template<class ExecutionPolicy, class ForwardIterator, class RandomAccessIterator>
  RandomAccessIterator
    partial_sort_copy(ExecutionPolicy&& exec,
                      ForwardIterator first, ForwardIterator last,
                      RandomAccessIterator result_first,
                      RandomAccessIterator result_last);

template<class InputIterator, class RandomAccessIterator,
         class Compare>
  constexpr RandomAccessIterator
    partial_sort_copy(InputIterator first, InputIterator last,
                      RandomAccessIterator result_first,
                      RandomAccessIterator result_last,
                      Compare comp);
template<class ExecutionPolicy, class ForwardIterator, class RandomAccessIterator,
         class Compare>
  RandomAccessIterator
    partial_sort_copy(ExecutionPolicy&& exec,
                      ForwardIterator first, ForwardIterator last,
                      RandomAccessIterator result_first,
                      RandomAccessIterator result_last,
                      Compare comp);

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I1, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I1> S1, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I2, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I2> S2,
         class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
  requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_­copyable [alg.req.ind.copy]")<I1, I2> && [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I2, Comp, Proj2> &&
           [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
  constexpr ranges::partial_sort_copy_result<I1, I2>
    ranges::partial_sort_copy(I1 first, S1 last, I2 result_first, S2 result_last,
                              Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R1, [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]") R2, class Comp = ranges::less,
         class Proj1 = identity, class Proj2 = identity>
  requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_­copyable [alg.req.ind.copy]")<iterator_t<R1>, iterator_t<R2>> &&
           [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R2>, Comp, Proj2> &&
           [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<Comp, projected<iterator_t<R1>, Proj1>,
                                      projected<iterator_t<R2>, Proj2>>
  constexpr ranges::partial_sort_copy_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
    ranges::partial_sort_copy(R1&& r, R2&& result_r, Comp comp = {},
                              Proj1 proj1 = {}, Proj2 proj2 = {});

template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I1, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<I1> S1,
         [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I2, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<I2> S2,
         class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
  requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_­copyable [alg.req.ind.copy]")<I1, I2> && [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<I2, Comp, Proj2> &&
            [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
  ranges::partial_sort_copy_result<I1, I2>
    ranges::partial_sort_copy(Ep&& exec, I1 first, S1 last, I2 result_first, S2 result_last,
                              Comp comp = {}, Proj1 proj1 = {},
                              Proj2 proj2 = {});
template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R1, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R2,
         class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
  requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_­copyable [alg.req.ind.copy]")<iterator_t<R1>, iterator_t<R2>> &&
           [sortable](alg.req.sortable#concept:sortable "24.3.7.8 Concept sortable [alg.req.sortable]")<iterator_t<R2>, Comp, Proj2> &&
           [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<Comp, projected<iterator_t<R1>, Proj1>,
                                      projected<iterator_t<R2>, Proj2>>
  ranges::partial_sort_copy_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
    ranges::partial_sort_copy(Ep&& exec, R1&& r, R2&& result_r, Comp comp = {},
                              Proj1 proj1 = {}, Proj2 proj2 = {});
`

[1](#partial.sort.copy-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9076)

Let N be min(last - first, result_last - result_first)[.](#partial.sort.copy-1.sentence-1)

Let comp be less{}, andproj1 and proj2 be identity{} for the overloads with no parameters by those names[.](#partial.sort.copy-1.sentence-2)

[2](#partial.sort.copy-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9082)

*Mandates*: For the overloads in namespace std,
the expression *first is writable ([[iterator.requirements.general]](iterator.requirements.general "24.3.1 General")) to result_first[.](#partial.sort.copy-2.sentence-1)

[3](#partial.sort.copy-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9088)

*Preconditions*: For the overloads in namespace std,RandomAccessIterator meets
the [*Cpp17ValueSwappable*](swappable.requirements#:Cpp17ValueSwappable "16.4.4.3 Swappable requirements [swappable.requirements]") requirements ([[swappable.requirements]](swappable.requirements "16.4.4.3 Swappable requirements")),
the type of *result_first meets
the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [31](utility.arg.requirements#tab:cpp17.moveconstructible "Table 31: Cpp17MoveConstructible requirements")) and[*Cpp17MoveAssignable*](utility.arg.requirements#:Cpp17MoveAssignable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [33](utility.arg.requirements#tab:cpp17.moveassignable "Table 33: Cpp17MoveAssignable requirements")) requirements[.](#partial.sort.copy-3.sentence-1)

[4](#partial.sort.copy-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9097)

For iterators a1 and b1 in [first, last), and
iterators x2 and y2 in [result_first, result_last),
after evaluating the assignment *y2 = *b1, let E be the value ofbool(invoke(comp, invoke(proj1, *a1), invoke(proj2, *y2))).

Then, after evaluating the assignment *x2 = *a1, E is equal tobool(invoke(comp, invoke(proj2, *x2), invoke(proj2, *y2))).

[*Note [1](#partial.sort.copy-note-1)*:

Writing a value from the input range into the output range does not affect
how it is ordered by comp and proj1 or proj2[.](#partial.sort.copy-4.sentence-2)

— *end note*]

[5](#partial.sort.copy-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9113)

*Effects*: Places the first N elements
as sorted with respect to comp and proj2 into the range [result_first, result_first + N)[.](#partial.sort.copy-5.sentence-1)

[6](#partial.sort.copy-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9119)

*Returns*: 

- [(6.1)](#partial.sort.copy-6.1)

  result_first + N for the overloads in namespace std[.](#partial.sort.copy-6.1.sentence-1)

- [(6.2)](#partial.sort.copy-6.2)

  {last, result_first + N} for
 the overloads in namespace ranges[.](#partial.sort.copy-6.2.sentence-1)

[7](#partial.sort.copy-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9129)

*Complexity*: Approximately (last - first) * log N comparisons,
and twice as many projections[.](#partial.sort.copy-7.sentence-1)

#### [26.8.2.5](#is.sorted) is_sorted [[is.sorted]](is.sorted)

[🔗](#lib:is_sorted)

`template<class ForwardIterator>
  constexpr bool is_sorted(ForwardIterator first, ForwardIterator last);
`

[1](#is.sorted-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9144)

*Effects*: Equivalent to: return is_sorted_until(first, last) == last;

[🔗](#lib:is_sorted_)

`template<class ExecutionPolicy, class ForwardIterator>
  bool is_sorted(ExecutionPolicy&& exec,
                 ForwardIterator first, ForwardIterator last);
`

[2](#is.sorted-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9157)

*Effects*: Equivalent to:return is_sorted_until(std::forward<ExecutionPolicy>(exec), first, last) == last;

[🔗](#lib:is_sorted__)

`template<class ForwardIterator, class Compare>
  constexpr bool is_sorted(ForwardIterator first, ForwardIterator last,
                           Compare comp);
`

[3](#is.sorted-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9173)

*Effects*: Equivalent to: return is_sorted_until(first, last, comp) == last;

[🔗](#lib:is_sorted___)

`template<class ExecutionPolicy, class ForwardIterator, class Compare>
  bool is_sorted(ExecutionPolicy&& exec,
                 ForwardIterator first, ForwardIterator last,
                 Compare comp);
`

[4](#is.sorted-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9188)

*Effects*: Equivalent to:return is_sorted_until(std::forward<ExecutionPolicy>(exec), first, last, comp) == last;

[🔗](#lib:is_sorted____)

`template<[forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_­iterator [iterator.concept.forward]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Comp = ranges::less>
  constexpr bool ranges::is_sorted(I first, S last, Comp comp = {}, Proj proj = {});
template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Comp = ranges::less>
  constexpr bool ranges::is_sorted(R&& r, Comp comp = {}, Proj proj = {});
`

[5](#is.sorted-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9207)

*Effects*: Equivalent to:return ranges​::​is_sorted_until(first, last, comp, proj) == last;

[🔗](#is.sorted-itemdecl:6)

`template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<I> S,
         class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Comp = ranges::less>
  bool ranges::is_sorted(Ep&& exec, I first, S last, Comp comp = {}, Proj proj = {});
template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Comp = ranges::less>
  bool ranges::is_sorted(Ep&& exec, R&& r, Comp comp = {}, Proj proj = {});
`

[6](#is.sorted-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9224)

*Effects*: Equivalent to:return ranges::is_sorted_until(std::forward<Ep>(exec), first, last, comp, proj) == last;

[🔗](#lib:is_sorted_until)

`template<class ForwardIterator>
  constexpr ForwardIterator
    is_sorted_until(ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator>
  ForwardIterator
    is_sorted_until(ExecutionPolicy&& exec,
                    ForwardIterator first, ForwardIterator last);

template<class ForwardIterator, class Compare>
  constexpr ForwardIterator
    is_sorted_until(ForwardIterator first, ForwardIterator last,
                    Compare comp);
template<class ExecutionPolicy, class ForwardIterator, class Compare>
  ForwardIterator
    is_sorted_until(ExecutionPolicy&& exec,
                    ForwardIterator first, ForwardIterator last,
                    Compare comp);

template<[forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_­iterator [iterator.concept.forward]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Comp = ranges::less>
  constexpr I ranges::is_sorted_until(I first, S last, Comp comp = {}, Proj proj = {});
template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Comp = ranges::less>
  constexpr borrowed_iterator_t<R>
    ranges::is_sorted_until(R&& r, Comp comp = {}, Proj proj = {});

template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_­access_­iterator [iterator.concept.random.access]") I, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<I> S,
         class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Comp = ranges::less>
  I ranges::is_sorted_until(Ep&& exec, I first, S last, Comp comp = {},
                    Proj proj = {});
template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Comp = ranges::less>
  borrowed_iterator_t<R>
    ranges::is_sorted_until(Ep&& exec, R&& r, Comp comp = {}, Proj proj = {});
`

[7](#is.sorted-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9272)

Let comp be less{} and proj be identity{} for the overloads with no parameters by those names[.](#is.sorted-7.sentence-1)

[8](#is.sorted-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9277)

*Returns*: The last iterator i in [first, last]
for which the range [first, i)
is sorted with respect to comp and proj[.](#is.sorted-8.sentence-1)

[9](#is.sorted-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9283)

*Complexity*: Linear[.](#is.sorted-9.sentence-1)