std::search_n

From Cppreference

Defined in header `<algorithm>`

template< class ForwardIterator, class Size, class T > ForwardIterator1 search_n( ForwardIterator first, ForwardIterator last, Size count, const T& value );	(1)

template< class ForwardIterator, class Size, class T, class BinaryPredicate > ForwardIterator1 search_n( ForwardIterator first, ForwardIterator last, Size count, const T& value, BinaryPredicate p );	(2)

Searches the range [first, last) for the first sequence of count identical elements, each equal to the given value value. The first version uses operator== to compare the elements, the second version uses the given binary predicate p.

The signature does not need to have const &, but the function must not modify the objects passed to it.
The type Type1 must be such that an object of type ForwardIterator1 can be dereferenced and then implicitly converted to Type1. The type Type2 must be such that an object of type T can be implicitly converted to Type2.

[edit] Return value

iterator to the beginning of the found sequence in the range [first, last). If no such sequence is found, last is returned.

[edit] Complexity

At most last - first applications of the predicate.

[edit] Equivalent function

First version

template<class ForwardIterator, class Size, class T>
ForwardIterator1 search_n(ForwardIterator first, ForwardIterator last,
                          Size count, const T& value)
{
    Size curr_count = 0;
    ForwardIterator result, t_last = first;
    std::advance(t_last, std::distance(first, last) - count + 1);
 
    for (; first != t_last; first++) {
        curr_count = 0;
        result = first;
        while (*first == value) {
            curr_count++;
            if (curr_count == count) {
                return result;
            }
            ++first;
        }
    }
    return last;
}

Second version

template<class ForwardIterator, class Size, class T, class BinaryPredicate>
ForwardIterator1 search_n(ForwardIterator first, ForwardIterator last,
                          Size count, const T& value, BinaryPredicate p)
{
    Size curr_count = 0;
    ForwardIterator result, t_last = first;
    std::advance(t_last, std::distance(first, last) - count + 1);
 
    for (; first != t_last; first++) {
        curr_count = 0;
        result = first;
        while (p(*first == value)) {
            curr_count++;
            if (curr_count == count) {
                return result;
            }
            ++first;
        }
    }
    return last;
}

[edit] Example

[edit] See also

find_end

finds the last sequence of elements in a certain range
(function template)

find find_if find_if_not (C++11)

finds the first element satisfying specific criteria
(function template)

search

searches for a range of elements
(function template)