std::multimap
Defined in header <map> | ||
|---|---|---|
template<
class Key,
class T,
class Compare = std::less<Key>,
class Allocator = std::allocator<std::pair<const Key, T> >
> class multimap;
| (1) | |
namespace pmr {
template <class Key, class T, class Compare = std::less<Key>>
using multimap = std::multimap<Key, T, Compare,
std::pmr::polymorphic_allocator<std::pair<const Key,T>>>;
}
| (2) | (since C++17) |
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 |
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mapped_type | T |
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value_type | std::pair<const Key, T> |
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size_type | Unsigned integer type (usually std::size_t) |
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difference_type | Signed integer type (usually std::ptrdiff_t) |
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key_compare | Compare |
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allocator_type | Allocator |
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reference |
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const_reference |
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pointer |
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const_pointer |
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iterator | LegacyBidirectionalIterator | ||||
const_iterator | Constant LegacyBidirectionalIterator | ||||
reverse_iterator | std::reverse_iterator<iterator> |
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const_reverse_iterator | std::reverse_iterator<const_iterator> |
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node_type(since C++17) | a specialization of node handle representing a container node |
Member classes
compares objects of type value_type (class) |
Member functions
constructs the multimap (public member function) |
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destructs the multimap (public member function) |
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| assigns values to the container (public member function) |
|
| returns the associated allocator (public member function) |
|
Iterators |
|
| returns an iterator to the beginning (public member function) |
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| returns an iterator to the end (public member function) |
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| returns a reverse iterator to the beginning (public member function) |
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| returns a reverse iterator to the end (public member function) |
|
Capacity |
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| checks whether the container is empty (public member function) |
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| returns the number of elements (public member function) |
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| returns the maximum possible number of elements (public member function) |
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Modifiers |
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| clears the contents (public member function) |
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| inserts elements or nodes (since C++17) (public member function) |
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(C++11) | constructs element in-place (public member function) |
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(C++11) | constructs elements in-place using a hint (public member function) |
| erases elements (public member function) |
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| swaps the contents (public member function) |
|
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(C++17) | extracts nodes from the container (public member function) |
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(C++17) | splices nodes from another container (public member function) |
Lookup |
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| returns the number of elements matching specific key (public member function) |
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| finds element with specific key (public member function) |
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(C++20) | checks if the container contains element with specific key (public member function) |
| returns range of elements matching a specific key (public member function) |
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| returns an iterator to the first element not less than the given key (public member function) |
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| returns an iterator to the first element greater than the given key (public member function) |
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Observers |
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| returns the function that compares keys (public member function) |
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| returns the function that compares keys in objects of type value_type (public member function) |
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Non-member functions
| lexicographically compares the values in the multimap (function template) |
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specializes the std::swap algorithm (function template) |
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(C++20) | Erases all elements satisfying specific criteria (function template) |
Deduction guides(since C++17)
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