Algorithms library - cppreference.com (original) (raw)

The algorithms library defines functions for a variety of purposes (e.g. searching, sorting, counting, manipulating) that operate on ranges of elements. Note that a range is defined as [first, last) where last refers to the element past the last element to inspect or modify.

Contents

[edit] Constrained algorithms (since C++20)

C++20 provides constrained versions of most algorithms in the namespace std::ranges. In these algorithms, a range can be specified as either an iterator-sentinel pair or as a single range argument, and projections and pointer-to-member callables are supported. Additionally, the return types of most algorithms have been changed to return all potentially useful information computed during the execution of the algorithm.

[edit] Execution policies (since C++17)

Most algorithms have overloads that accept execution policies. The standard library algorithms support several execution policies, and the library provides corresponding execution policy types and objects. Users may select an execution policy statically by invoking a parallel algorithm with an execution policy object of the corresponding type.

Standard library implementations (but not the users) may define additional execution policies as an extension. The semantics of parallel algorithms invoked with an execution policy object of implementation-defined type is implementation-defined.

Parallel version of algorithms (except for std::for_each and std::for_each_n) are allowed to make arbitrary copies of elements from ranges, as long as both std::is_trivially_copy_constructible_v<T> and std::is_trivially_destructible_v<T> are true, where T is the type of elements.

Defined in header
Defined in namespace std::execution
sequenced_policyparallel_policyparallel_unsequenced_policyunsequenced_policy(C++17)(C++17)(C++17)(C++20) execution policy types (class) [edit]
seqparpar_unsequnseq(C++17)(C++17)(C++17)(C++20) global execution policy objects (constant) [edit]
Defined in namespace std
is_execution_policy(C++17) test whether a class represents an execution policy (class template) [edit]
Feature-test macro Value Std Feature
__cpp_lib_parallel_algorithm 201603L (C++17) Parallel algorithms
__cpp_lib_execution 201603L (C++17) Execution policies
201902L (C++20) std::execution::unsequenced_policy

[edit] Non-modifying sequence operations

[edit] Batch operations

[edit] Search operations

Defined in header
all_ofany_ofnone_of(C++11)(C++11)(C++11) checks if a predicate is true for all, any or none of the elements in a range (function template) [edit]
ranges::all_ofranges::any_ofranges::none_of(C++20)(C++20)(C++20) checks if a predicate is true for all, any or none of the elements in a range(algorithm function object)[edit]
ranges::containsranges::contains_subrange(C++23)(C++23) checks if the range contains the given element or subrange(algorithm function object)[edit]
findfind_iffind_if_not(C++11) finds the first element satisfying specific criteria (function template) [edit]
ranges::findranges::find_ifranges::find_if_not(C++20)(C++20)(C++20) finds the first element satisfying specific criteria(algorithm function object)[edit]
ranges::find_lastranges::find_last_ifranges::find_last_if_not(C++23)(C++23)(C++23) finds the last element satisfying specific criteria(algorithm function object)[edit]
find_end finds the last sequence of elements in a certain range (function template) [edit]
ranges::find_end(C++20) finds the last sequence of elements in a certain range(algorithm function object)[edit]
find_first_of searches for any one of a set of elements (function template) [edit]
ranges::find_first_of(C++20) searches for any one of a set of elements(algorithm function object)[edit]
adjacent_find finds the first two adjacent items that are equal (or satisfy a given predicate) (function template) [edit]
ranges::adjacent_find(C++20) finds the first two adjacent items that are equal (or satisfy a given predicate)(algorithm function object)[edit]
countcount_if returns the number of elements satisfying specific criteria (function template) [edit]
ranges::countranges::count_if(C++20)(C++20) returns the number of elements satisfying specific criteria(algorithm function object)[edit]
mismatch finds the first position where two ranges differ (function template) [edit]
ranges::mismatch(C++20) finds the first position where two ranges differ(algorithm function object)[edit]
equal determines if two sets of elements are the same (function template) [edit]
ranges::equal(C++20) determines if two sets of elements are the same(algorithm function object)[edit]
search searches for the first occurrence of a range of elements (function template) [edit]
ranges::search(C++20) searches for the first occurrence of a range of elements(algorithm function object)[edit]
search_n searches for the first occurrence of a number consecutive copies of an element in a range (function template) [edit]
ranges::search_n(C++20) searches for the first occurrence of a number consecutive copies of an element in a range(algorithm function object)[edit]
ranges::starts_with(C++23) checks whether a range starts with another range(algorithm function object)[edit]
ranges::ends_with(C++23) checks whether a range ends with another range(algorithm function object)[edit]

[edit] Fold operations (since C++23)

Defined in header
ranges::fold_left(C++23) left-folds a range of elements(algorithm function object)[edit]
ranges::fold_left_first(C++23) left-folds a range of elements using the first element as an initial value(algorithm function object)[edit]
ranges::fold_right(C++23) right-folds a range of elements(algorithm function object)[edit]
ranges::fold_right_last(C++23) right-folds a range of elements using the last element as an initial value(algorithm function object)[edit]
ranges::fold_left_with_iter(C++23) left-folds a range of elements, and returns a pair (iterator, value)(algorithm function object)[edit]
ranges::fold_left_first_with_iter(C++23) left-folds a range of elements using the first element as an initial value, and returns a pair (iterator, optional)(algorithm function object)[edit]

[edit] Modifying sequence operations

[edit] Copy operations

Defined in header
copycopy_if(C++11) copies a range of elements to a new location (function template) [edit]
ranges::copyranges::copy_if(C++20)(C++20) copies a range of elements to a new location(algorithm function object)[edit]
copy_n(C++11) copies a number of elements to a new location (function template) [edit]
ranges::copy_n(C++20) copies a number of elements to a new location(algorithm function object)[edit]
copy_backward copies a range of elements in backwards order (function template) [edit]
ranges::copy_backward(C++20) copies a range of elements in backwards order(algorithm function object)[edit]
move(C++11) moves a range of elements to a new location (function template) [edit]
ranges::move(C++20) moves a range of elements to a new location(algorithm function object)[edit]
move_backward(C++11) moves a range of elements to a new location in backwards order (function template) [edit]
ranges::move_backward(C++20) moves a range of elements to a new location in backwards order(algorithm function object)[edit]

[edit] Swap operations

Defined in header (until C++11)
Defined in header (since C++11)
Defined in header <string_view>
swap swaps the values of two objects (function template) [edit]
Defined in header
swap_ranges swaps two ranges of elements (function template) [edit]
ranges::swap_ranges(C++20) swaps two ranges of elements(algorithm function object)[edit]
iter_swap swaps the elements pointed to by two iterators (function template) [edit]

[edit] Transformation operations

Defined in header
transform applies a function to a range of elements, storing results in a destination range (function template) [edit]
ranges::transform(C++20) applies a function to a range of elements(algorithm function object)[edit]
replacereplace_if replaces all values satisfying specific criteria with another value (function template) [edit]
ranges::replaceranges::replace_if(C++20)(C++20) replaces all values satisfying specific criteria with another value(algorithm function object)[edit]
replace_copyreplace_copy_if copies a range, replacing elements satisfying specific criteria with another value (function template) [edit]
ranges::replace_copyranges::replace_copy_if(C++20)(C++20) copies a range, replacing elements satisfying specific criteria with another value(algorithm function object)[edit]

[edit] Generation operations

Defined in header
fill copy-assigns the given value to every element in a range (function template) [edit]
ranges::fill(C++20) assigns a range of elements a certain value(algorithm function object)[edit]
fill_n copy-assigns the given value to N elements in a range (function template) [edit]
ranges::fill_n(C++20) assigns a value to a number of elements(algorithm function object)[edit]
generate assigns the results of successive function calls to every element in a range (function template) [edit]
ranges::generate(C++20) saves the result of a function in a range(algorithm function object)[edit]
generate_n assigns the results of successive function calls to N elements in a range (function template) [edit]
ranges::generate_n(C++20) saves the result of N applications of a function(algorithm function object)[edit]

[edit] Removing operations

Defined in header
removeremove_if removes elements satisfying specific criteria (function template) [edit]
ranges::removeranges::remove_if(C++20)(C++20) removes elements satisfying specific criteria(algorithm function object)[edit]
remove_copyremove_copy_if copies a range of elements omitting those that satisfy specific criteria (function template) [edit]
ranges::remove_copyranges::remove_copy_if(C++20)(C++20) copies a range of elements omitting those that satisfy specific criteria(algorithm function object)[edit]
unique removes consecutive duplicate elements in a range (function template) [edit]
ranges::unique(C++20) removes consecutive duplicate elements in a range(algorithm function object)[edit]
unique_copy creates a copy of some range of elements that contains no consecutive duplicates (function template) [edit]
ranges::unique_copy(C++20) creates a copy of some range of elements that contains no consecutive duplicates(algorithm function object)[edit]

[edit] Order-changing operations

Defined in header
reverse reverses the order of elements in a range (function template) [edit]
ranges::reverse(C++20) reverses the order of elements in a range(algorithm function object)[edit]
reverse_copy creates a copy of a range that is reversed (function template) [edit]
ranges::reverse_copy(C++20) creates a copy of a range that is reversed(algorithm function object)[edit]
rotate rotates the order of elements in a range (function template) [edit]
ranges::rotate(C++20) rotates the order of elements in a range(algorithm function object)[edit]
rotate_copy copies and rotate a range of elements (function template) [edit]
ranges::rotate_copy(C++20) copies and rotate a range of elements(algorithm function object)[edit]
shift_leftshift_right(C++20) shifts elements in a range (function template) [edit]
ranges::shift_leftranges::shift_right(C++23) shifts elements in a range(algorithm function object)[edit]
random_shuffleshuffle(until C++17)(C++11) randomly re-orders elements in a range (function template) [edit]
ranges::shuffle(C++20) randomly re-orders elements in a range(algorithm function object)[edit]

[edit] Sampling operations

[edit] Requirements

Some algorithms require the sequence represented by the arguments to be “sorted” or “partitioned”. The behavior is undefined if the requirement is not met.

A sequence is sorted with respect to a comparator comp if for every iterator iter pointing to the sequence and every non-negative integer n such that iter + n[1] is a valid iterator pointing to an element of the sequence, comp(*(iter + n), *iter) == false[1]. (until C++20)
A sequence is sorted with respect to comp and proj for a comparator comp and projection proj if for every iterator iter pointing to the sequence and every non-negative integer n such that iter + n[1] is a valid iterator pointing to an element of the sequence, bool(std::invoke(comp, std::invoke(proj, *(iter + n)), std::invoke(proj, *iter)))[1] is false.A sequence is sorted with respect to a comparator comp if the sequence is sorted with respect to comp and std::identity{} (the identity projection). (since C++20)

A sequence [start, finish) is partitioned with respect to an expression f(e) if there exists an integer n such that for all i in [​0​, std::distance(start, finish)), f(*(start + i))[1] is true if and only if i < n.

  1. ↑ 1.0 1.1 1.2 1.3 1.4 iter + n simply means “the result of iter being incremented n times”, regardless of whether iter is a random access iterator.

[edit] Partitioning operations

Defined in header
is_partitioned(C++11) determines if the range is partitioned by the given predicate (function template) [edit]
ranges::is_partitioned(C++20) determines if the range is partitioned by the given predicate(algorithm function object)[edit]
partition divides a range of elements into two groups (function template) [edit]
ranges::partition(C++20) divides a range of elements into two groups(algorithm function object)[edit]
partition_copy(C++11) copies a range dividing the elements into two groups (function template) [edit]
ranges::partition_copy(C++20) copies a range dividing the elements into two groups(algorithm function object)[edit]
stable_partition divides elements into two groups while preserving their relative order (function template) [edit]
ranges::stable_partition(C++20) divides elements into two groups while preserving their relative order(algorithm function object)[edit]
partition_point(C++11) locates the partition point of a partitioned range (function template) [edit]
ranges::partition_point(C++20) locates the partition point of a partitioned range(algorithm function object)[edit]

[edit] Sorting operations

Defined in header
sort sorts a range into ascending order (function template) [edit]
ranges::sort(C++20) sorts a range into ascending order(algorithm function object)[edit]
stable_sort sorts a range of elements while preserving order between equal elements (function template) [edit]
ranges::stable_sort(C++20) sorts a range of elements while preserving order between equal elements(algorithm function object)[edit]
partial_sort sorts the first N elements of a range (function template) [edit]
ranges::partial_sort(C++20) sorts the first N elements of a range(algorithm function object)[edit]
partial_sort_copy copies and partially sorts a range of elements (function template) [edit]
ranges::partial_sort_copy(C++20) copies and partially sorts a range of elements(algorithm function object)[edit]
is_sorted(C++11) checks whether a range is sorted into ascending order (function template) [edit]
ranges::is_sorted(C++20) checks whether a range is sorted into ascending order(algorithm function object)[edit]
is_sorted_until(C++11) finds the largest sorted subrange (function template) [edit]
ranges::is_sorted_until(C++20) finds the largest sorted subrange(algorithm function object)[edit]
nth_element partially sorts the given range making sure that it is partitioned by the given element (function template) [edit]
ranges::nth_element(C++20) partially sorts the given range making sure that it is partitioned by the given element(algorithm function object)[edit]

[edit] Binary search operations (on partitioned ranges)

Defined in header
lower_bound returns an iterator to the first element not less than the given value (function template) [edit]
ranges::lower_bound(C++20) returns an iterator to the first element not less than the given value(algorithm function object)[edit]
upper_bound returns an iterator to the first element greater than a certain value (function template) [edit]
ranges::upper_bound(C++20) returns an iterator to the first element greater than a certain value(algorithm function object)[edit]
equal_range returns range of elements matching a specific key (function template) [edit]
ranges::equal_range(C++20) returns range of elements matching a specific key(algorithm function object)[edit]
binary_search determines if an element exists in a partially-ordered range (function template) [edit]
ranges::binary_search(C++20) determines if an element exists in a partially-ordered range(algorithm function object)[edit]

[edit] Set operations (on sorted ranges)

Defined in header
includes returns true if one sequence is a subsequence of another (function template) [edit]
ranges::includes(C++20) returns true if one sequence is a subsequence of another(algorithm function object)[edit]
set_union computes the union of two sets (function template) [edit]
ranges::set_union(C++20) computes the union of two sets(algorithm function object)[edit]
set_intersection computes the intersection of two sets (function template) [edit]
ranges::set_intersection(C++20) computes the intersection of two sets(algorithm function object)[edit]
set_difference computes the difference between two sets (function template) [edit]
ranges::set_difference(C++20) computes the difference between two sets(algorithm function object)[edit]
set_symmetric_difference computes the symmetric difference between two sets (function template) [edit]
ranges::set_symmetric_difference(C++20) computes the symmetric difference between two sets(algorithm function object)[edit]

[edit] Merge operations (on sorted ranges)

[edit] Heap operations

A random access range [first, last) is a heap with respect to a comparator comp if bool(comp(first[(i - 1) / 2], first[i])) is false for all integer i in (​0​, last - first). (until C++20)
A random access range [first, last) is a _heap with respect to comp and proj_ for a comparator comp and projection proj if bool(std::invoke(comp, std::invoke(proj, first[(i - 1) / 2]), std::invoke(proj, first[i])) is false for all integer i in (​0​, last - first).A random access range [first, last) is a _heap with respect to a comparator comp_ if the range is a heap with respect to comp and std::identity{} (the identity projection). (since C++20)

A heap can be created by std::make_heap and ranges::make_heap(since C++20).

For more properties of heap, see max heap.

Defined in header
push_heap adds an element to a max heap (function template) [edit]
ranges::push_heap(C++20) adds an element to a max heap(algorithm function object)[edit]
pop_heap removes the largest element from a max heap (function template) [edit]
ranges::pop_heap(C++20) removes the largest element from a max heap(algorithm function object)[edit]
make_heap creates a max heap out of a range of elements (function template) [edit]
ranges::make_heap(C++20) creates a max heap out of a range of elements(algorithm function object)[edit]
sort_heap turns a max heap into a range of elements sorted in ascending order (function template) [edit]
ranges::sort_heap(C++20) turns a max heap into a range of elements sorted in ascending order(algorithm function object)[edit]
is_heap(C++11) checks if the given range is a max heap (function template) [edit]
ranges::is_heap(C++20) checks if the given range is a max heap(algorithm function object)[edit]
is_heap_until(C++11) finds the largest subrange that is a max heap (function template) [edit]
ranges::is_heap_until(C++20) finds the largest subrange that is a max heap(algorithm function object)[edit]

[edit] Minimum/maximum operations

Defined in header
max returns the greater of the given values (function template) [edit]
ranges::max(C++20) returns the greater of the given values(algorithm function object)[edit]
max_element returns the largest element in a range (function template) [edit]
ranges::max_element(C++20) returns the largest element in a range(algorithm function object)[edit]
min returns the smaller of the given values (function template) [edit]
ranges::min(C++20) returns the smaller of the given values(algorithm function object)[edit]
min_element returns the smallest element in a range (function template) [edit]
ranges::min_element(C++20) returns the smallest element in a range(algorithm function object)[edit]
minmax(C++11) returns the smaller and larger of two elements (function template) [edit]
ranges::minmax(C++20) returns the smaller and larger of two elements(algorithm function object)[edit]
minmax_element(C++11) returns the smallest and the largest elements in a range (function template) [edit]
ranges::minmax_element(C++20) returns the smallest and the largest elements in a range(algorithm function object)[edit]
clamp(C++17) clamps a value between a pair of boundary values (function template) [edit]
ranges::clamp(C++20) clamps a value between a pair of boundary values(algorithm function object)[edit]

[edit] Lexicographical comparison operations

[edit] Permutation operations

Defined in header
next_permutation generates the next greater lexicographic permutation of a range of elements (function template) [edit]
ranges::next_permutation(C++20) generates the next greater lexicographic permutation of a range of elements(algorithm function object)[edit]
prev_permutation generates the next smaller lexicographic permutation of a range of elements (function template) [edit]
ranges::prev_permutation(C++20) generates the next smaller lexicographic permutation of a range of elements(algorithm function object)[edit]
is_permutation(C++11) determines if a sequence is a permutation of another sequence (function template) [edit]
ranges::is_permutation(C++20) determines if a sequence is a permutation of another sequence(algorithm function object)[edit]

[edit] Numeric operations

Defined in header
iota(C++11) fills a range with successive increments of the starting value (function template) [edit]
ranges::iota(C++23) fills a range with successive increments of the starting value(algorithm function object)[edit]
accumulate sums up or folds a range of elements (function template) [edit]
inner_product computes the inner product of two ranges of elements (function template) [edit]
adjacent_difference computes the differences between adjacent elements in a range (function template) [edit]
partial_sum computes the partial sum of a range of elements (function template) [edit]
reduce(C++17) similar to std::accumulate, except out of order (function template) [edit]
exclusive_scan(C++17) similar to std::partial_sum, excludes the ith input element from the ith sum (function template) [edit]
inclusive_scan(C++17) similar to std::partial_sum, includes the ith input element in the ith sum (function template) [edit]
transform_reduce(C++17) applies an invocable, then reduces out of order (function template) [edit]
transform_exclusive_scan(C++17) applies an invocable, then calculates exclusive scan (function template) [edit]
transform_inclusive_scan(C++17) applies an invocable, then calculates inclusive scan (function template) [edit]

[edit] Operations on uninitialized memory

Defined in header
uninitialized_copy copies a range of objects to an uninitialized area of memory (function template) [edit]
ranges::uninitialized_copy(C++20) copies a range of objects to an uninitialized area of memory(algorithm function object)[edit]
uninitialized_copy_n(C++11) copies a number of objects to an uninitialized area of memory (function template) [edit]
ranges::uninitialized_copy_n(C++20) copies a number of objects to an uninitialized area of memory(algorithm function object)[edit]
uninitialized_fill copies an object to an uninitialized area of memory, defined by a range (function template) [edit]
ranges::uninitialized_fill(C++20) copies an object to an uninitialized area of memory, defined by a range(algorithm function object)[edit]
uninitialized_fill_n copies an object to an uninitialized area of memory, defined by a start and a count (function template) [edit]
ranges::uninitialized_fill_n(C++20) copies an object to an uninitialized area of memory, defined by a start and a count(algorithm function object)[edit]
uninitialized_move(C++17) moves a range of objects to an uninitialized area of memory (function template) [edit]
ranges::uninitialized_move(C++20) moves a range of objects to an uninitialized area of memory(algorithm function object)[edit]
uninitialized_move_n(C++17) moves a number of objects to an uninitialized area of memory (function template) [edit]
ranges::uninitialized_move_n(C++20) moves a number of objects to an uninitialized area of memory(algorithm function object)[edit]
uninitialized_default_construct(C++17) constructs objects by default-initialization in an uninitialized area of memory, defined by a range (function template) [edit]
ranges::uninitialized_default_construct(C++20) constructs objects by default-initialization in an uninitialized area of memory, defined by a range(algorithm function object)[edit]
uninitialized_default_construct_n(C++17) constructs objects by default-initialization in an uninitialized area of memory, defined by a start and a count (function template) [edit]
ranges::uninitialized_default_construct_n(C++20) constructs objects by default-initialization in an uninitialized area of memory, defined by a start and count(algorithm function object)[edit]
uninitialized_value_construct(C++17) constructs objects by value-initialization in an uninitialized area of memory, defined by a range (function template) [edit]
ranges::uninitialized_value_construct(C++20) constructs objects by value-initialization in an uninitialized area of memory, defined by a range(algorithm function object)[edit]
uninitialized_value_construct_n(C++17) constructs objects by value-initialization in an uninitialized area of memory, defined by a start and a count (function template) [edit]
ranges::uninitialized_value_construct_n(C++20) constructs objects by value-initialization in an uninitialized area of memory, defined by a start and a count(algorithm function object)[edit]
destroy(C++17) destroys a range of objects (function template) [edit]
ranges::destroy(C++20) destroys a range of objects(algorithm function object)[edit]
destroy_n(C++17) destroys a number of objects in a range (function template) [edit]
ranges::destroy_n(C++20) destroys a number of objects in a range(algorithm function object)[edit]
destroy_at(C++17) destroys an object at a given address (function template) [edit]
ranges::destroy_at(C++20) destroys an object at a given address(algorithm function object)[edit]
construct_at(C++20) creates an object at a given address (function template) [edit]
ranges::construct_at(C++20) creates an object at a given address(algorithm function object)[edit]

[edit] Random number generation (since C++26)

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_algorithm_iterator_requirements 202207L (C++23) Ranges iterators as inputs to non-Ranges algorithms
__cpp_lib_clamp 201603L (C++17) std::clamp
__cpp_lib_constexpr_algorithms 201806L (C++20) Constexpr for algorithms
202306L (C++26) Constexpr stable sorting
__cpp_lib_algorithm_default_value_type 202403L (C++26) List-initialization for algorithms
__cpp_lib_freestanding_algorithm 202311L (C++26) Freestanding facilities in
__cpp_lib_robust_nonmodifying_seq_ops 201304L (C++14) Making non-modifying sequence operations more robust (two-range overloads for std::mismatch, std::equal and std::is_permutation)
__cpp_lib_sample 201603L (C++17) std::sample
__cpp_lib_shift 201806L (C++20) std::shift_left and std::shift_right

[edit] C library

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 193 C++98 heap required *first to be the largest element there can be elementsequal to *first
LWG 2150 C++98 the definition of a sorted sequence was incorrect corrected
LWG 2166 C++98 the heap requirement did not match thedefinition of max heap closely enough requirement improved

[edit] See also