std::map
| Defined in header <map>
|
||
| template< class Key, |
(1) | |
| namespace pmr { template <class Key, class T, class Compare = std::less<Key>> |
(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 concept, 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 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
|
| ||||
const_reference
|
| ||||
pointer
|
| ||||
const_pointer
|
| ||||
iterator
|
BidirectionalIterator | ||||
const_iterator
|
Constant bidirectional iterator | ||||
reverse_iterator
|
std::reverse_iterator<iterator> | ||||
const_reverse_iterator
|
std::reverse_iterator<const_iterator> | ||||
node_type
|
a specialization of node handle representing a container node (since C++17) | ||||
insert_return_type
|
type describing the result of inserting a node_type, a specialization of template <class Iterator, class NodeType> struct /*unspecified*/ { Iterator position; bool inserted; NodeType node; }; iterator and node_type. (since C++17) |
Member classes
compares objects of type value_type (class) |
Member functions
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 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) | |
| 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) | |
Non-member functions
| lexicographically compares the values in the map (function template) | |
| specializes the std::swap algorithm (function template) |