From cppreference.com
std::pair<iterator,iterator>equal_range(constKey&key); (1) (since C++23)std::pair<const_iterator,const_iterator>equal_range(constKey&key)const; (2) (since C++23)template<classK>std::pair<iterator,iterator>equal_range(constK&x); (3)(since C++23)template<classK>std::pair<const_iterator,const_iterator>equal_range(constK&x)const; (4) (since C++23)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().
1,2) Compares the keys to key.
3,4) Compares the keys to the value x. This overload participates in overload resolution only if the qualified-id Compare::is_transparent is valid and denotes a type. It allows calling this function without constructing an instance of Key.
Parameters
key - key value to compare the elements to x - alternative value that can be compared to KeyReturn value
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, past-the-end (see end()) iterator is returned as the first element. Similarly if there are no elements greater than key, past-the-end iterator is returned as the second element.
Since
and unhinted
always insert at the upper bound, the order of equivalent elements in the equal range is the order of insertion unless hinted
or
was used to insert an element at a different position.
Complexity
Logarithmic in the size of the container.
Example
Run this code
#include<iostream>#include<flat_set>template<typenameI>voidprint_equal_range(Ifirst,Ilb,Iub,Ilast){for(Ii{first};i!=lb;++i)std::cout<<*i<<' ';std::cout<<"[ ";for(Ii{lb};i!=ub;++i)std::cout<<*i<<' ';std::cout<<") ";for(Ii{ub};i!=last;++i)std::cout<<*i<<' ';std::cout<<'\n';}intmain(){std::flat_multiset<int>c{4,3,2,1,3,3};std::cout<<"c = ";print_equal_range(begin(c),begin(c),end(c),end(c));for(intkey{};key!=6;++key){std::cout<<"key = "<<key<<"; equal range = ";constauto[lb,ub]=c.equal_range(key);print_equal_range(begin(c),lb,ub,end(c));}}Output:
c = [ 1 2 3 3 3 4 ) key = 0; equal range = [ ) 1 2 3 3 3 4 key = 1; equal range = [ 1 ) 2 3 3 3 4 key = 2; equal range = 1 [ 2 ) 3 3 3 4 key = 3; equal range = 1 2 [ 3 3 3 ) 4 key = 4; equal range = 1 2 3 3 3 [ 4 ) key = 5; equal range = 1 2 3 3 3 4 [ ) See also
finds element with specific key
(public member function)
checks if the container contains element with specific key
(public member function)
returns the number of elements matching 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)
finds the range of elements matching the given value using binary search
(function template & algorithm function object)
(C++20)