std::equal_range

From Cppreference

Returns a range containing all elements equal to value in the sorted range [first, last). The range is defined by two iterators, one pointing to the first element that is not less than value and another pointing to the first element greater than value. The first iterator may be alternatively obtained with lower_bound(), the second - with upper_bound().

The first version uses operator< to compare the elements, the second version uses the given comparison function comp.

[edit] Parameters

[edit] Return value

std::pair containing a pair of iterators defining the wanted range, the first pointing to the first element that is not less than value and the second pointing to the first element greater than value.

If there are no elements not less than value, last is returned as the first element. Similarly if there are no elements greater than value, last is returned as the second element

[edit] Complexity

logarithmic in the distance between first and last

[edit] Equivalent function

template<class ForwardIterator, class T 
std::pair<ForwardIterator,ForwardIterator> 
    equal_range(ForwardIterator first, ForwardIterator last,
                const T& value)
{
    return std::make_pair(std::lower_bound(first, last, value),
                          std::upper_bound(first, last, value));
}

template<class ForwardIterator, class T, class Compare>
std::pair<ForwardIterator,ForwardIterator> 
    equal_range(ForwardIterator first, ForwardIterator last,
                const T& value, Compare comp);
{
    return std::make_pair(std::lower_bound(first, last, value, comp),
                          std::upper_bound(first, last, value, comp));
}

[edit] Example

[edit] See also