| 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; |
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 integral 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> |
Member classes
compares objects of type value_type (class) |
Member functions
constructs the map (public member function) | |
| (destructor)
| destructs the map (public member function) |
| operator=
| 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 (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) | |
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) |
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