Defined in header <map> | ||
|---|---|---|
template<
class Key,
class T,
class Compare = std::less<Key>,
class Allocator = std::allocator<std::pair<const Key, T> >
> class map;
| (1) | |
namespace pmr {
template <class Key, class T, class Compare = std::less<Key>>
using map = std::map<Key, T, Compare,
std::pmr::polymorphic_allocator<std::pair<const Key,T>>>
}
| (2) | (since C++17) |
std::map is a sorted associative container that contains key-value pairs with unique keys. Keys are sorted by using the comparison function Compare. Search, removal, and insertion operations have logarithmic complexity. Maps are usually implemented as red-black trees.
Everywhere the standard library uses the Compare requirements, uniqueness is determined by using the equivalence relation. In imprecise terms, two objects a and b are considered equivalent (not unique) if neither compares less than the other: !comp(a, b) && !comp(b, a).
std::map meets the requirements of Container, AllocatorAwareContainer, AssociativeContainer and ReversibleContainer.
| 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 |
|
||||
const_reference |
|
||||
pointer |
|
||||
const_pointer |
|
||||
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 | ||||
insert_return_type(since C++17) | type describing the result of inserting a node_type, a specialization of template <class Iter, class NodeType> struct /*unspecified*/ {
Iter position;
bool inserted;
NodeType node;
};iterator and node_type. |
compares objects of type value_type (class) |
constructs the map (public member function) |
|
destructs the map (public member function) |
|
| assigns values to the container (public member function) |
|
| returns the associated allocator (public member function) |
|
Element access |
|
|
(C++11) | access specified element with bounds checking (public member function) |
| access or insert specified element (public member function) |
|
Iterators |
|
| returns an iterator to the beginning (public member function) |
|
| returns an iterator to the end (public member function) |
|
| returns a reverse iterator to the beginning (public member function) |
|
| returns a reverse iterator to the end (public member function) |
|
Capacity |
|
| checks whether the container is empty (public member function) |
|
| returns the number of elements (public member function) |
|
| returns the maximum possible number of elements (public member function) |
|
Modifiers |
|
| clears the contents (public member function) |
|
| inserts elements or nodes (since C++17) (public member function) |
|
|
(C++17) | inserts an element or assigns to the current element if the key already exists (public member function) |
|
(C++11) | constructs element in-place (public member function) |
|
(C++11) | constructs elements in-place using a hint (public member function) |
|
(C++17) | inserts in-place if the key does not exist, does nothing if the key exists (public member function) |
| erases elements (public member function) |
|
| swaps the contents (public member function) |
|
|
(C++17) | extracts nodes from the container (public member function) |
|
(C++17) | splices nodes from another container (public member function) |
Lookup |
|
| returns the number of elements matching specific key (public member function) |
|
| finds element with specific key (public member function) |
|
|
(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) |
|
| returns an iterator to the first element not less than the given key (public member function) |
|
| returns an iterator to the first element greater than the given key (public member function) |
|
Observers |
|
| returns the function that compares keys (public member function) |
|
| returns the function that compares keys in objects of type value_type (public member function) |
|
| lexicographically compares the values in the map (function template) |
|
specializes the std::swap algorithm (function template) |
|
|
(C++20) | Erases all elements satisfying specific criteria (function template) |
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