std::multimap<Key,T,Compare,Allocator>::equal_range

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().

# Declarations

std::pair<iterator, iterator> equal_range( const Key& key );

std::pair<const_iterator, const_iterator> equal_range( const Key& key ) const;

template< class K >
std::pair<iterator, iterator> equal_range( const K& x );

(since C++14)

template< class K >
std::pair<const_iterator, const_iterator> equal_range( const K& x ) const;

(since C++14)

# Parameters

key: key value to compare the elements to
x: alternative value that can be compared to Key

# 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 key and the second pointing to the first element greater than key.

# Notes

Feature-test macro Value Std Feature __cpp_lib_generic_associative_lookup 201304L (C++14) Heterogeneous comparison lookup in associative containers, for overloads (3,4)

# Example

#include <iostream>
#include <map>
 
int main()
{
    std::multimap<int, char> dict
    {
        {1, 'A'},
        {2, 'B'},
        {2, 'C'},
        {2, 'D'},
        {4, 'E'},
        {3, 'F'}
    };
 
    auto range = dict.equal_range(2);
 
    for (auto i = range.first; i != range.second; ++i)
        std::cout << i->first << ": " << i->second << '\n';
}