# Algorithms library

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< cpp

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.

##### Execution policies

Most algorithms have overloads that accept execution policies. The standard library algorithms support three execution policies: sequential, parallel, and parallel+vector, 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: std::execution::seq, std::execution::par, or std::execution::par_unseq.

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.

Defined in header `<execution>`
Defined in namespace `execution`
sequenced_policy parallel_policy parallel_unsequenced_policy (C++17)(C++17)(C++17) | execution policy types (class)
seq par par_unseq (C++17)(C++17)(C++17) | global execution policy objects (constant)
is_execution_policy (C++17) | test whether a class represents an execution policy (class template)

(since C++17)

##### Non-modifying sequence operations

Defined in header `<algorithm>`
all_of any_of none_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)
for_each | applies a function to a range of elements (function template)
for_each_n (C++17) | applies a function object to the first n elements of a sequence (function template)
count count_if | returns the number of elements satisfying specific criteria (function template)
mismatch | finds the first position where two ranges differ (function template)
equal | determines if two sets of elements are the same (function template)
find find_if find_if_not (C++11) | finds the first element satisfying specific criteria (function template)
find_end | finds the last sequence of elements in a certain range (function template)
find_first_of | searches for any one of a set of elements (function template)
adjacent_find | finds the first two adjacent items that are equal (or satisfy a given predicate) (function template)
search | searches for a range of elements (function template)
search_n | searches for a number consecutive copies of an element in a range (function template)

##### Modifying sequence operations

Defined in header `<algorithm>`
copy copy_if (C++11) | copies a range of elements to a new location (function template)
copy_n (C++11) | copies a number of elements to a new location (function template)
copy_backward | copies a range of elements in backwards order (function template)
move (C++11) | moves a range of elements to a new location (function template)
move_backward (C++11) | moves a range of elements to a new location in backwards order (function template)
fill | copy-assigns the given value to every element in a range (function template)
fill_n | copy-assigns the given value to N elements in a range (function template)
transform | applies a function to a range of elements (function template)
generate | assigns the results of successive function calls to every element in a range (function template)
generate_n | assigns the results of successive function calls to N elements in a range (function template)
remove remove_if | removes elements satisfying specific criteria (function template)
remove_copy remove_copy_if | copies a range of elements omitting those that satisfy specific criteria (function template)
replace replace_if | replaces all values satisfying specific criteria with another value (function template)
replace_copy replace_copy_if | copies a range, replacing elements satisfying specific criteria with another value (function template)
swap | swaps the values of two objects (function template)
swap_ranges | swaps two ranges of elements (function template)
iter_swap | swaps the elements pointed to by two iterators (function template)
reverse | reverses the order of elements in a range (function template)
reverse_copy | creates a copy of a range that is reversed (function template)
rotate | rotates the order of elements in a range (function template)
rotate_copy | copies and rotate a range of elements (function template)
random_shuffle shuffle (until C++17)(C++11) | randomly re-orders elements in a range (function template)
sample (C++17) | selects n random elements from a sequence (function template)
unique | removes consecutive duplicate elements in a range (function template)
unique_copy | creates a copy of some range of elements that contains no consecutive duplicates (function template)

##### Partitioning operations

Defined in header `<algorithm>`
is_partitioned (C++11) | determines if the range is partitioned by the given predicate (function template)
partition | divides a range of elements into two groups (function template)
partition_copy (C++11) | copies a range dividing the elements into two groups (function template)
stable_partition | divides elements into two groups while preserving their relative order (function template)
partition_point (C++11) | locates the partition point of a partitioned range (function template)

##### Sorting operations

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

##### Binary search operations (on sorted ranges)

Defined in header `<algorithm>`
lower_bound | returns an iterator to the first element not less than the given value (function template)
upper_bound | returns an iterator to the first element greater than a certain value (function template)
binary_search | determines if an element exists in a certain range (function template)
equal_range | returns range of elements matching a specific key (function template)

##### Set operations (on sorted ranges)

Defined in header `<algorithm>`
merge | merges two sorted ranges (function template)
inplace_merge | merges two ordered ranges in-place (function template)
includes | returns true if one set is a subset of another (function template)
set_difference | computes the difference between two sets (function template)
set_intersection | computes the intersection of two sets (function template)
set_symmetric_difference | computes the symmetric difference between two sets (function template)
set_union | computes the union of two sets (function template)

##### Heap operations

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

##### Minimum/maximum operations

Defined in header `<algorithm>`
max | returns the greater of the given values (function template)
max_element | returns the largest element in a range (function template)
min | returns the smaller of the given values (function template)
min_element | returns the smallest element in a range (function template)
minmax (C++11) | returns the smaller and larger of two elements (function template)
minmax_element (C++11) | returns the smallest and the largest elements in a range (function template)
clamp (C++17) | clamps a value between a pair of boundary values (function template)
lexicographical_compare | returns true if one range is lexicographically less than another (function template)
is_permutation (C++11) | determines if a sequence is a permutation of another sequence (function template)
next_permutation | generates the next greater lexicographic permutation of a range of elements (function template)
prev_permutation | generates the next smaller lexicographic permutation of a range of elements (function template)

##### Numeric operations

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

##### Operations on uninitialized memory

Defined in header `<memory>`
uninitialized_copy | copies a range of objects to an uninitialized area of memory (function template)
uninitialized_copy_n (C++11) | copies a number of objects to an uninitialized area of memory (function template)
uninitialized_fill | copies an object to an uninitialized area of memory, defined by a range (function template)
uninitialized_fill_n | copies an object to an uninitialized area of memory, defined by a start and a count (function template)
uninitialized_move (C++17) | moves a range of objects to an uninitialized area of memory (function template)
uninitialized_move_n (C++17) | moves a number of objects to an uninitialized area of memory (function template)
uninitialized_default_construct (C++17) | constructs objects by default-initialization in an uninitialized area of memory, defined by a range (function template)
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)
uninitialized_value_construct (C++17) | constructs objects by value-initialization in an uninitialized area of memory, defined by a range (function template)
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)
destroy_at (C++17) | destroys an object at a given address (function template)
destroy (C++17) | destroys a range of objects (function template)
destroy_n (C++17) | destroys a number of objects in a range (function template)

##### C library

Defined in header `<cstdlib>`
qsort | sorts a range of elements with unspecified type (function)
bsearch | searches an array for an element of unspecified type (function)

### See also

C documentation for Algorithms

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