std::multimap (3) - Linux Manuals

std::multimap: std::multimap


std::multimap - std::multimap


Defined in header <map>
class Key,
class T, (1)
class Compare = std::less<Key>,
class Allocator = std::allocator<std::pair<const Key, T> >
> class multimap;
namespace pmr {
template <class Key, class T, class Compare = std::less<Key>>
using multimap = std::multimap<Key, T, Compare, (2) (since C++17)
std::pmr::polymorphic_allocator<std::pair<const Key,T>>>;

Multimap is an associative container that contains a sorted list of key-value pairs, while permitting multiple entries with the same key. Sorting is done according to the comparison function Compare, applied to the keys. Search, insertion, and removal operations have logarithmic complexity.
The order of the key-value pairs whose keys compare equivalent is the order of insertion and does not change. (since C++11)
Everywhere the standard library uses the Compare requirements, equivalence is determined by using the equivalence relation as described on Compare. In imprecise terms, two objects a and b are considered equivalent if neither compares less than the other: !comp(a, b) && !comp(b, a).
std::multimap meets the requirements of Container, AllocatorAwareContainer, AssociativeContainer and ReversibleContainer.

Member types

Member type Definition
key_type Key
mapped_type T
value_type std::pair<const Key, T>
size_type Unsigned integer type (usually std::size_t)
difference_type Signed integer type (usually std::ptrdiff_t)
key_compare Compare
allocator_type Allocator

reference Allocator::reference (until C++11)
                       value_type& (since C++11)

const_reference Allocator::const_reference (until C++11)
                       const value_type& (since C++11)

pointer Allocator::pointer (until C++11)
                       std::allocator_traits<Allocator>::pointer (since C++11)

const_pointer Allocator::const_pointer (until C++11)
                       std::allocator_traits<Allocator>::const_pointer (since C++11)

iterator LegacyBidirectionalIterator
const_iterator Constant LegacyBidirectionalIterator
reverse_iterator std::reverse_iterator<iterator>
const_reverse_iterator std::reverse_iterator<const_iterator>
node_type(since C++17) a specialization of node_handle representing a container node

Member classes

              compares objects of type value_type
value_compare (class)

Member functions

              constructs the multimap
constructor (public member function)
              destructs the multimap
destructor (public member function)
              assigns values to the container
operator= (public member function)
              returns the associated allocator
get_allocator (public member function)


begin returns an iterator to the beginning
cbegin (public member function)

end_ returns an iterator to the end
cend (public member function)

rbegin returns a reverse iterator to the beginning
crbegin (public member function)

rend returns a reverse iterator to the end
crend (public member function)


              checks whether the container is empty
empty (public member function)
              returns the number of elements
size (public member function)
              returns the maximum possible number of elements
max_size (public member function)


              clears the contents
clear (public member function)
              inserts elements
              or nodes
insert (since C++17)
              (public member function)

emplace constructs element in-place
              (public member function)

emplace_hint constructs elements in-place using a hint
              (public member function)
              erases elements
erase (public member function)
              swaps the contents
swap (public member function)

extract extracts nodes from the container
              (public member function)

merge splices nodes from another container
              (public member function)


              returns the number of elements matching specific key
count (public member function)
              finds element with specific key
find (public member function)

contains checks if the container contains element with specific key
              (public member function)
              returns range of elements matching a specific key
equal_range (public member function)
              returns an iterator to the first element not less than the given key
lower_bound (public member function)
              returns an iterator to the first element greater than the given key
upper_bound (public member function)


              returns the function that compares keys
key_comp (public member function)
              returns the function that compares keys in objects of type value_type
value_comp (public member function)

Non-member functions

operator!= lexicographically compares the values in the multimap
operator< (function template)
                         specializes the std::swap algorithm
std::swap(std::multimap) (function template)

erase_if(std::multimap) Erases all elements satisfying specific criteria
                         (function template)

Deduction_guides(since C++17)