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std::map

From cppreference.com
< cpp‎ | container
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.

Contents

[edit] Member types

Member type Definition
key_type Key [edit]
mapped_type T [edit]
value_type std::pair<const Key, T> [edit]
size_type Unsigned integral type (usually std::size_t) [edit]
difference_type Signed integer type (usually std::ptrdiff_t) [edit]
key_compare Compare [edit]
allocator_type Allocator [edit]
reference
Allocator::reference (until C++11)
value_type& (since C++11)
[edit]
const_reference
Allocator::const_reference (until C++11)
const value_type& (since C++11)
[edit]
pointer
Allocator::pointer (until C++11)
std::allocator_traits<Allocator>::pointer (since C++11)
[edit]
const_pointer
Allocator::const_pointer (until C++11)
std::allocator_traits<Allocator>::const_pointer (since C++11)
[edit]
iterator BidirectionalIterator [edit]
const_iterator Constant bidirectional iterator [edit]
reverse_iterator std::reverse_iterator<iterator> [edit]
const_reverse_iterator std::reverse_iterator<const_iterator> [edit]

[edit] Member classes

compares objects of type value_type
(class) [edit]

[edit] Member functions

constructs the map
(public member function) [edit]
destructs the map
(public member function) [edit]
assigns values to the container
(public member function) [edit]
returns the associated allocator
(public member function) [edit]
Element access
(C++11)
access specified element with bounds checking
(public member function) [edit]
access specified element
(public member function) [edit]
Iterators
returns an iterator to the beginning
(public member function) [edit]
returns an iterator to the end
(public member function) [edit]
returns a reverse iterator to the beginning
(public member function) [edit]
returns a reverse iterator to the end
(public member function) [edit]
Capacity
checks whether the container is empty
(public member function) [edit]
returns the number of elements
(public member function) [edit]
returns the maximum possible number of elements
(public member function) [edit]
Modifiers
clears the contents
(public member function) [edit]
inserts elements
(public member function) [edit]
inserts an element or assigns to the current element if the key already exists
(public member function) [edit]
(C++11)
constructs element in-place
(public member function) [edit]
constructs elements in-place using a hint
(public member function) [edit]
inserts in-place if the key does not exist, does nothing if the key exists
(public member function) [edit]
erases elements
(public member function) [edit]
swaps the contents
(public member function) [edit]
Lookup
returns the number of elements matching specific key
(public member function) [edit]
finds element with specific key
(public member function) [edit]
returns range of elements matching a specific key
(public member function) [edit]
returns an iterator to the first element not less than the given key
(public member function) [edit]
returns an iterator to the first element greater than the given key
(public member function) [edit]
Observers
returns the function that compares keys
(public member function) [edit]
returns the function that compares keys in objects of type value_type
(public member function) [edit]

[edit] Non-member functions

lexicographically compares the values in the map
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]