std::pair<iterator,iterator> equal_range( const Key& key );  (1)  
std::pair<const_iterator,const_iterator> equal_range( const Key& key ) const;  (2)  
template< class K > std::pair<iterator,iterator> equal_range( const K& x );  (3)  (since C++14) 
template< class K > std::pair<const_iterator,const_iterator> equal_range( const K& x ) const;  (4)  (since C++14) 
Returns a range containing all elements with the given key in the container. The range is defined by two iterators, one pointing to the first element that is not less than key
and another pointing to the first element greater than key
. Alternatively, the first iterator may be obtained with lower_bound()
, and the second with upper_bound()
.
key
.x
. This overload only participates in overload resolution if the qualifiedid Compare::is_transparent
is valid and denotes a type. They allow calling this function without constructing an instance of Key
. key    key value to compare the elements to 
x    alternative value that can be compared to Key 
std::pair
containing a pair of iterators defining the wanted range: the first pointing to the first element that is not less than key
and the second pointing to the first element greater than key
.
If there are no elements not less than key
, pasttheend (see end()
) iterator is returned as the first element. Similarly if there are no elements greater than key
, pasttheend iterator is returned as the second element.
Since insert always inserts at the upper bound, the order of equivalent elements in the equal range is the order of insertion.  (since C++11) 
Logarithmic in the size of the container.
finds element with specific key (public member function) 

returns an iterator to the first element greater than the given key (public member function) 

returns an iterator to the first element not less than the given key (public member function) 
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