<algorithm>

Defines C++ Standard Library container template functions that perform algorithms.

Syntax

(see links below for specific algorithm syntax)

Note

The <algorithm> library also uses the #include <initializer_list> statement.

Remarks

The C++ Standard Library algorithms can operate on various data structures. The data structures that they can operate on include not only the C++ Standard Library container classes such as vector and list, but also user-defined data structures and arrays of elements, as long as they satisfy the requirements of a particular algorithm. C++ Standard Library algorithms achieve this level of generality by accessing and traversing the elements of a container indirectly through iterators.

C++ Standard Library algorithms process iterator ranges that are typically specified by their beginning or ending positions. The ranges referred to must be valid in the sense that all iterators in the ranges must be dereferenceable and, within the sequences of each range, the last position must be reachable from the first by incrementing the iterator.

Starting in C++20, most of the algorithms defined in <algorithm> are also available in a form that takes a range. For example, rather than call sort(v1.begin(), v1.end(), greater<int>());, you can call ranges::sort(v1, greater<int>());

The C++ Standard Library algorithms can work with different types of container objects at the same time. Two suffixes have been used to convey information about the purpose of the algorithms:

• The _if suffix indicates that the algorithm is used with function objects that operate on the values of the elements rather than on the elements themselves. For example, the find_if algorithm looks for elements whose values satisfy the criterion specified by a function object, whereas the find algorithm searches for a particular value.

• The _copy suffix indicates that the algorithm generally modifies copied values rather than copy modified values. In other words, they don't modify the source range's elements but put the results into an output range/iterator. For example, the reverse algorithm reverses the order of the elements within a range, whereas the reverse_copy algorithm copies the reversed result into a destination range.

C++ Standard Library algorithms are often classified into groups to indicate their purpose or requirements. These include modifying algorithms that change the value of elements as compared with non-modifying algorithms that don't. Mutating algorithms change the order of elements, but not the values of their elements. Removing algorithms can eliminate elements from a range or a copy of a range. Sorting algorithms reorder the elements in a range in various ways and sorted range algorithms only act on ranges whose elements have been sorted in a particular way.

The C++ Standard Library numeric algorithms that are provided for numerical processing have their own header file <numeric>, and function objects and adaptors are defined in the header <functional>. Function objects that return Boolean values are known as predicates. The default binary predicate is the comparison operator<. In general, the elements being ordered need to be less than comparable so that, given any two elements, it can be determined either that they're equivalent (in the sense that neither is less than the other) or that one is less than the other. This results in an ordering among the nonequivalent elements.

Algorithms

Name	Description
adjacent_find	Searches for two adjacent elements that are either equal or satisfy a specified condition.
all_of	Returns true when a condition is present at each element in the given range.
any_of	Returns true when a condition is present at least once in the specified range of elements.
binary_search	Tests whether there is an element in a sorted range that is equal to a specified value or that is equivalent to it in a sense specified by a binary predicate.
clamp
copy	Assigns the values of elements from a source range to a destination range, iterating through the source sequence of elements and assigning them new positions in a forward direction.
copy_backward	Assigns the values of elements from a source range to a destination range, iterating through the source sequence of elements and assigning them new positions in a backward direction.
copy_if	Copy all elements in a given range that test true for a specified condition
copy_n	Copies a specified number of elements.
count	Returns the number of elements in a range whose values match a specified value.
count_if	Returns the number of elements in a range whose values match a specified condition.
equal	Compares two ranges element by element either for equality or equivalence in a sense specified by a binary predicate.
equal_range	Finds a pair of positions in an ordered range, the first less than or equivalent to the position of a specified element and the second greater than the element's position, where the sense of equivalence or ordering used to establish the positions in the sequence may be specified by a binary predicate.
fill	Assigns the same new value to every element in a specified range.
fill_n	Assigns a new value to a specified number of elements in a range starting with a particular element.
find	Locates the position of the first occurrence of an element in a range that has a specified value.
find_end	Looks in a range for the last subsequence that is identical to a specified sequence or that is equivalent in a sense specified by a binary predicate.
find_first_of	Searches for the first occurrence of any of several values within a target range or for the first occurrence of any of several elements that are equivalent in a sense specified by a binary predicate to a specified set of the elements.
find_if	Locates the position of the first occurrence of an element in a range that satisfies a specified condition.
find_if_not	Returns the first element in the indicated range that doesn't satisfy a condition.
for_each	Applies a specified function object to each element in a forward order within a range and returns the function object.
for_each_n
generate	Assigns the values generated by a function object to each element in a range.
generate_n	Assigns the values generated by a function object to a specified number of elements in a range and returns to the position one past the last assigned value.
includes	Tests whether one sorted range contains all the elements contained in a second sorted range, where the ordering or equivalence criterion between elements may be specified by a binary predicate.
inplace_merge	Combines the elements from two consecutive sorted ranges into a single sorted range, where the ordering criterion may be specified by a binary predicate.
is_heap	Returns true if the elements in the specified range form a heap.
is_heap_until	Returns true if the specified range forms a heap until the last element.
is_partitioned	Returns true if all the elements in the given range that test true for a condition come before any elements that test false.
is_permutation	Determines whether the elements in a given range form a valid permutation.
is_sorted	Returns true if the elements in the specified range are in sorted order.
is_sorted_until	Returns true if the elements in the specified range are in sorted order.
iter_swap	Exchanges two values referred to by a pair of specified iterators.
lexicographical_compare	Compares element by element between two sequences to determine which is lesser of the two.
lower_bound	Finds the position of the first element in an ordered range that has a value greater than or equivalent to a specified value, where the ordering criterion may be specified by a binary predicate.
make_heap	Converts elements from a specified range into a heap in which the first element is the largest and for which a sorting criterion may be specified with a binary predicate.
max	Compares two objects and returns the larger of the two, where the ordering criterion may be specified by a binary predicate.
max_element	Finds the first occurrence of largest element in a specified range where the ordering criterion may be specified by a binary predicate.
merge	Combines all the elements from two sorted source ranges into a single, sorted destination range, where the ordering criterion may be specified by a binary predicate.
min	Compares two objects and returns the lesser of the two, where the ordering criterion may be specified by a binary predicate.
min_element	Finds the first occurrence of smallest element in a specified range where the ordering criterion may be specified by a binary predicate.
minmax	Compares two input parameters and returns them as a pair, in order of least to greatest.
minmax_element	Performs the work performed by min_element and max_element in one call.
mismatch	Compares two ranges element by element either for equality or equivalent in a sense specified by a binary predicate and locates the first position where a difference occurs.
<alg> move	Move elements associated with a specified range.
move_backward	Moves the elements of one iterator to another. The move starts with the last element in a specified range, and ends with the first element in that range.
next_permutation	Reorders the elements in a range so that the original ordering is replaced by the lexicographically next greater permutation if it exists, where the sense of next may be specified with a binary predicate.
none_of	Returns true when a condition is never present among elements in the given range.
nth_element	Partitions a range of elements, correctly locating the nth element of the sequence in the range so that all the elements in front of it are less than or equal to it and all the elements that follow it in the sequence are greater than or equal to it.
partial_sort	Arranges a specified number of the smaller elements in a range into a nondescending order or according to an ordering criterion specified by a binary predicate.
partial_sort_copy	Copies elements from a source range into a destination range where the source elements are ordered by either less than or another specified binary predicate.
partition	Classifies elements in a range into two disjoint sets, with those elements satisfying a unary predicate preceding those that fail to satisfy it.
partition_copy	Copies elements for which a condition is true to one destination, and for which the condition is false to another. The elements must come from a specified range.
partition_point	Returns the first element in the given range that doesn't satisfy the condition. The elements are sorted so that those that satisfy the condition come before those that don't.
pop_heap	Removes the largest element from the front of a heap to the next-to-last position in the range and then forms a new heap from the remaining elements.
prev_permutation	Reorders the elements in a range so that the original ordering is replaced by the lexicographically next greater permutation if it exists, where the sense of next may be specified with a binary predicate.
push_heap	Adds an element that is at the end of a range to an existing heap consisting of the prior elements in the range.
random_shuffle	Rearranges a sequence of N elements in a range into one of N! possible arrangements selected at random.
remove	Eliminates a specified value from a given range without disturbing the order of the remaining elements and returning the end of a new range free of the specified value.
remove_copy	Copies elements from a source range to a destination range, except that elements of a specified value aren't copied, without disturbing the order of the remaining elements and returning the end of a new destination range.
remove_copy_if	Copies elements from a source range to a destination range, except that satisfying a predicate aren't copied, without disturbing the order of the remaining elements and returning the end of a new destination range.
remove_if	Eliminates elements that satisfy a predicate from a given range without disturbing the order of the remaining elements and returning the end of a new range free of the specified value.
replace	Examines each element in a range and replaces it if it matches a specified value.
replace_copy	Examines each element in a source range and replaces it if it matches a specified value while copying the result into a new destination range.
replace_copy_if	Examines each element in a source range and replaces it if it satisfies a specified predicate while copying the result into a new destination range.
replace_if	Examines each element in a range and replaces it if it satisfies a specified predicate.
reverse	Reverses the order of the elements within a range.
reverse_copy	Reverses the order of the elements within a source range while copying them into a destination range
rotate	Exchanges the elements in two adjacent ranges.
rotate_copy	Exchanges the elements in two adjacent ranges within a source range and copies the result to a destination range.
sample
search	Searches for the first occurrence of a sequence within a target range whose elements are equal to those in a given sequence of elements or whose elements are equivalent in a sense specified by a binary predicate to the elements in the given sequence.
search_n	Searches for the first subsequence in a range that of a specified number of elements having a particular value or a relation to that value as specified by a binary predicate.
set_difference	Unites all of the elements that belong to one sorted source range, but not to a second sorted source range, into a single, sorted destination range, where the ordering criterion may be specified by a binary predicate.
set_intersection	Unites all of the elements that belong to both sorted source ranges into a single, sorted destination range, where the ordering criterion may be specified by a binary predicate.
set_symmetric_difference	Unites all of the elements that belong to one, but not both, of the sorted source ranges into a single, sorted destination range, where the ordering criterion may be specified by a binary predicate.
set_union	Unites all of the elements that belong to at least one of two sorted source ranges into a single, sorted destination range, where the ordering criterion may be specified by a binary predicate.
sort	Arranges the elements in a specified range into a nondescending order or according to an ordering criterion specified by a binary predicate.
shuffle	Shuffles (rearranges) elements for a given range using a random number generator.
sort_heap	Converts a heap into a sorted range.
stable_partition	Classifies elements in a range into two disjoint sets, with those elements satisfying a unary predicate preceding those that fail to satisfy it, preserving the relative order of equivalent elements.
stable_sort	Arranges the elements in a specified range into a nondescending order or according to an ordering criterion specified by a binary predicate and preserves the relative ordering of equivalent elements.
swap	Exchanges the values of the elements between two types of objects, assigning the contents of the first object to the second object and the contents of the second to the first.
swap_ranges	Exchanges the elements of one range with the elements of another, equal sized range.
transform	Applies a specified function object to each element in a source range or to a pair of elements from two source ranges and copies the return values of the function object into a destination range.
unique	Removes duplicate elements that are next to each other in a specified range.
unique_copy	Copies elements from a source range into a destination range except for the duplicate elements that are next to each other.
upper_bound	Finds the position of the first element in an ordered range that has a value that is greater than a specified value, where the ordering criterion may be specified by a binary predicate.

See also

Header Files Reference
Thread Safety in the C++ Standard Library
C++ Standard Library Reference