# 28 Algorithms library [algorithms]

## 28.5 Non-modifying sequence operations [alg.nonmodifying]

### 28.5.1 All of [alg.all_of]

```template <class InputIterator, class Predicate> bool all_of(InputIterator first, InputIterator last, Predicate pred); template <class ExecutionPolicy, class ForwardIterator, class Predicate> bool all_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); ```

Returns: true if [first, last) is empty or if pred(*i) is true for every iterator i in the range [first, last), and false otherwise.

Complexity: At most last - first applications of the predicate.

### 28.5.2 Any of [alg.any_of]

```template <class InputIterator, class Predicate> bool any_of(InputIterator first, InputIterator last, Predicate pred); template <class ExecutionPolicy, class ForwardIterator, class Predicate> bool any_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); ```

Returns: false if [first, last) is empty or if there is no iterator i in the range [first, last) such that pred(*i) is true, and true otherwise.

Complexity: At most last - first applications of the predicate.

### 28.5.3 None of [alg.none_of]

```template <class InputIterator, class Predicate> bool none_of(InputIterator first, InputIterator last, Predicate pred); template <class ExecutionPolicy, class ForwardIterator, class Predicate> bool none_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); ```

Returns: true if [first, last) is empty or if pred(*i) is false for every iterator i in the range [first, last), and false otherwise.

Complexity: At most last - first applications of the predicate.

### 28.5.4 For each [alg.foreach]

```template<class InputIterator, class Function> Function for_each(InputIterator first, InputIterator last, Function f); ```

Requires: Function shall meet the requirements of MoveConstructible. [Note: Function need not meet the requirements of CopyConstructible. end note]

Effects: Applies f to the result of dereferencing every iterator in the range [first, last), starting from first and proceeding to last - 1. [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.end note]

Returns: f.

Complexity: Applies f exactly last - first times.

Remarks: If f returns a result, the result is ignored.

```template<class ExecutionPolicy, class ForwardIterator, class Function> void for_each(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Function f); ```

Requires: Function shall meet the requirements of CopyConstructible.

Effects: Applies f to the result of dereferencing every iterator in the range [first, last). [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator. end note]

Complexity: Applies f exactly last - first times.

Remarks: If f returns a result, the result is ignored. Implementations do not have the freedom granted under [algorithms.parallel.exec] to make arbitrary copies of elements from the input sequence.

[Note: Does not return a copy of its Function parameter, since parallelization may not permit efficient state accumulation. end note]

```template<class InputIterator, class Size, class Function> InputIterator for_each_n(InputIterator first, Size n, Function f); ```

Requires: Function shall meet the requirements of MoveConstructible [Note: Function need not meet the requirements of CopyConstructible. end note]

Requires: n >= 0.

Effects: Applies f to the result of dereferencing every iterator in the range [first, first + n) in order. [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator. end note]

Returns: first + n.

Remarks: If f returns a result, the result is ignored.

```template<class ExecutionPolicy, class ForwardIterator, class Size, class Function> ForwardIterator for_each_n(ExecutionPolicy&& exec, ForwardIterator first, Size n, Function f); ```

Requires: Function shall meet the requirements of CopyConstructible.

Requires: n >= 0.

Effects: Applies f to the result of dereferencing every iterator in the range [first, first + n). [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator. end note]

Returns: first + n.

Remarks: If f returns a result, the result is ignored. Implementations do not have the freedom granted under [algorithms.parallel.exec] to make arbitrary copies of elements from the input sequence.

### 28.5.5 Find [alg.find]

```template<class InputIterator, class T> InputIterator find(InputIterator first, InputIterator last, const T& value); template<class ExecutionPolicy, class ForwardIterator, class T> ForwardIterator find(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& value); template<class InputIterator, class Predicate> InputIterator find_if(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> ForwardIterator find_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<class InputIterator, class Predicate> InputIterator find_if_not(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> ForwardIterator find_if_not(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); ```

Returns: The first iterator i in the range [first, last) for which the following corresponding conditions hold: *i == value, pred(*i) != false, pred(*i) == false. Returns last if no such iterator is found.

Complexity: At most last - first applications of the corresponding predicate.

### 28.5.6 Find end [alg.find.end]

```template<class ForwardIterator1, class ForwardIterator2> ForwardIterator1 find_end(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator1 find_end(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 find_end(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 find_end(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); ```

Effects: Finds a subsequence of equal values in a sequence.

Returns: The last iterator i in the range [first1, last1 - (last2 - first2)) such that for every non-negative integer n < (last2 - first2), the following corresponding conditions hold: *(i + n) == *(​first2 + n), pred(*(i + n), *(first2 + n)) != false. Returns last1 if [first2, last2) is empty or if no such iterator is found.

Complexity: At most (last2 - first2) * (last1 - first1 - (last2 - first2) + 1) applications of the corresponding predicate.

### 28.5.7 Find first [alg.find.first.of]

```template<class InputIterator, class ForwardIterator> InputIterator find_first_of(InputIterator first1, InputIterator last1, ForwardIterator first2, ForwardIterator last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator1 find_first_of(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class InputIterator, class ForwardIterator, class BinaryPredicate> InputIterator find_first_of(InputIterator first1, InputIterator last1, ForwardIterator first2, ForwardIterator last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 find_first_of(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); ```

Effects: Finds an element that matches one of a set of values.

Returns: The first iterator i in the range [first1, last1) such that for some iterator j in the range [first2, last2) the following conditions hold: *i == *j, pred(*i,*j) != false. Returns last1 if [first2, last2) is empty or if no such iterator is found.

Complexity: At most (last1-first1) * (last2-first2) applications of the corresponding predicate.

```template<class ForwardIterator> ForwardIterator adjacent_find(ForwardIterator first, ForwardIterator last); template<class ExecutionPolicy, class ForwardIterator> ForwardIterator adjacent_find(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last); template<class ForwardIterator, class BinaryPredicate> ForwardIterator adjacent_find(ForwardIterator first, ForwardIterator last, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator, class BinaryPredicate> ForwardIterator adjacent_find(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, BinaryPredicate pred); ```

Returns: The first iterator i such that both i and i + 1 are in the range [first, last) for which the following corresponding conditions hold: *i == *(i + 1), pred(*i, *(i + 1)) != false. Returns last if no such iterator is found.

Complexity: For the overloads with no ExecutionPolicy, exactly min((i - first) + 1, (last - first) - 1) applications of the corresponding predicate, where i is adjacent_­find's return value. For the overloads with an ExecutionPolicy, O(last - first) applications of the corresponding predicate.

### 28.5.9 Count [alg.count]

```template<class InputIterator, class T> typename iterator_traits<InputIterator>::difference_type count(InputIterator first, InputIterator last, const T& value); template<class ExecutionPolicy, class ForwardIterator, class T> typename iterator_traits<ForwardIterator>::difference_type count(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& value); template<class InputIterator, class Predicate> typename iterator_traits<InputIterator>::difference_type count_if(InputIterator first, InputIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> typename iterator_traits<ForwardIterator>::difference_type count_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); ```

Effects: Returns the number of iterators i in the range [first, last) for which the following corresponding conditions hold: *i == value, pred(*i) != false.

Complexity: Exactly last - first applications of the corresponding predicate.

### 28.5.10 Mismatch [mismatch]

```template<class InputIterator1, class InputIterator2> pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, BinaryPredicate pred); template<class InputIterator1, class InputIterator2> pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> pair<ForwardIterator1, ForwardIterator2> mismatch(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); ```

Remarks: If last2 was not given in the argument list, it denotes first2 + (last1 - first1) below.

Returns: A pair of iterators first1 + n and first2 + n, where n is the smallest integer such that, respectively,

• !(*(first1 + n) == *(first2 + n)) or

• pred(*(first1 + n), *(first2 + n)) == false,

or min(last1 - first1, last2 - first2) if no such integer exists.

Complexity: At most min(last1 - first1, last2 - first2) applications of the corresponding predicate.

### 28.5.11 Equal [alg.equal]

```template<class InputIterator1, class InputIterator2> bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, BinaryPredicate pred); template<class InputIterator1, class InputIterator2> bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class InputIterator1, class InputIterator2, class BinaryPredicate> bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> bool equal(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); ```

Remarks: If last2 was not given in the argument list, it denotes first2 + (last1 - first1) below.

Returns: If last1 - first1 != last2 - first2, return false. Otherwise return true if for every iterator i in the range [first1, last1) the following corresponding conditions hold: *i == *(first2 + (i - first1)), pred(*i, *(first2 + (i - first1))) != false. Otherwise, returns false.

Complexity:

• For the overloads with no ExecutionPolicy,

• if InputIterator1 and InputIterator2 meet the requirements of random access iterators ([random.access.iterators]) and last1 - first1 != last2 - first2, then no applications of the corresponding predicate; otherwise,

• at most min(last1 - first1,last2 - first2) applications of the corresponding predicate.

• For the overloads with no ExecutionPolicy,

• if ForwardIterator1 and ForwardIterator2 meet the requirements of random access iterators and last1 - first1 != last2 - first2, then no applications of the corresponding predicate; otherwise,

• O(min(last1 - first1,last2 - first2)) applications of the corresponding predicate.

### 28.5.12 Is permutation [alg.is_permutation]

```template<class ForwardIterator1, class ForwardIterator2> bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, BinaryPredicate pred); template<class ForwardIterator1, class ForwardIterator2> bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); ```

Requires: ForwardIterator1 and ForwardIterator2 shall have the same value type. The comparison function shall be an equivalence relation.

Remarks: If last2 was not given in the argument list, it denotes first2 + (last1 - first1) below.

Returns: If last1 - first1 != last2 - first2, return false. Otherwise return true if there exists a permutation of the elements in the range [first2, first2 + (last1 - first1)), beginning with ForwardIterator2 begin, such that equal(first1, last1, begin) returns true or equal(first1, last1, begin, pred) returns true; otherwise, returns false.

Complexity: No applications of the corresponding predicate if ForwardIterator1 and ForwardIterator2 meet the requirements of random access iterators and last1 - first1 != last2 - first2. Otherwise, exactly last1 - first1 applications of the corresponding predicate if equal(​first1, last1, first2, last2) would return true if pred was not given in the argument list or equal(first1, last1, first2, last2, pred) would return true if pred was given in the argument list; otherwise, at worst O(N2), where N has the value last1 - first1.

### 28.5.13 Search [alg.search]

```template<class ForwardIterator1, class ForwardIterator2> ForwardIterator1 search(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> ForwardIterator1 search(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 search(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 search(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred); ```

Effects: Finds a subsequence of equal values in a sequence.

Returns: The first iterator i in the range [first1, last1 - (last2-first2)) such that for every non-negative integer n less than last2 - first2 the following corresponding conditions hold: *(i + n) == *(first2 + n), pred(*(i + n), *(first2 + n)) != false. Returns first1 if [first2, last2) is empty, otherwise returns last1 if no such iterator is found.

Complexity: At most (last1 - first1) * (last2 - first2) applications of the corresponding predicate.

```template<class ForwardIterator, class Size, class T> ForwardIterator search_n(ForwardIterator first, ForwardIterator last, Size count, const T& value); template<class ForwardIterator, class Size, class T, class BinaryPredicate> ForwardIterator search_n(ForwardIterator first, ForwardIterator last, Size count, const T& value, BinaryPredicate pred); template<class ExecutionPolicy, class ForwardIterator, class Size, class T> ForwardIterator search_n(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Size count, const T& value); template<class ExecutionPolicy, class ForwardIterator, class Size, class T, class BinaryPredicate> ForwardIterator search_n(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Size count, const T& value, BinaryPredicate pred); ```

Requires: The type Size shall be convertible to integral type ([conv.integral], [class.conv]).

Effects: Finds a subsequence of equal values in a sequence.

Returns: The first iterator i in the range [first, last-count) such that for every non-negative integer n less than count the following corresponding conditions hold: *(i + n) == value, pred(*(i + n),value) != false. Returns last if no such iterator is found.

Complexity: At most last - first applications of the corresponding predicate.

```template<class ForwardIterator, class Searcher> ForwardIterator search(ForwardIterator first, ForwardIterator last, const Searcher& searcher); ```

Effects: Equivalent to: return searcher(first, last).first;

Remarks: Searcher need not meet the CopyConstructible requirements.