The function equal_range is used to find the range as a pair where an element can be inserted without altering the order.
template<class ForwardIterator, class T> pair<ForwardIterator, ForwardIterator> equal_range (ForwardIterator first, ForwardIterator last, const T& value); template<class ForwardIterator, class T, class Compare> pair<ForwardIterator, ForwardIterator> equal_range (ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
The range as a pair<> where the element can be inserted is returned.