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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.

`std::map` meets the requirements of `Container`, `AllocatorAwareContainer`, `AssociativeContainer` and `ReversibleContainer`.

### [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

value_compare | compares objects of type `value_type` (class) [edit]

### [edit] Member functions

(constructor) | constructs the `map` (public member function) [edit]
(destructor) | destructs the `map` (public member function) [edit]
operator= | assigns values to the container (public member function) [edit]
get_allocator | returns the associated allocator (public member function) [edit]
##### Element access
at (C++11) | access specified element with bounds checking (public member function) [edit]
operator[] | access specified element (public member function) [edit]
##### Iterators
begin cbegin | returns an iterator to the beginning (public member function) [edit]
end cend | returns an iterator to the end (public member function) [edit]
rbegin crbegin | returns a reverse iterator to the beginning (public member function) [edit]
rend crend | returns a reverse iterator to the end (public member function) [edit]
##### Capacity
empty | checks whether the container is empty (public member function) [edit]
size | returns the number of elements (public member function) [edit]
max_size | returns the maximum possible number of elements (public member function) [edit]
##### Modifiers
clear | clears the contents (public member function) [edit]
insert | inserts elements (public member function) [edit]
emplace (C++11) | constructs element in-place (public member function) [edit]
emplace_hint (C++11) | constructs elements in-place using a hint (public member function) [edit]
erase | erases elements (public member function) [edit]
swap | swaps the contents (public member function) [edit]
##### Lookup
count | returns the number of elements matching specific key (public member function) [edit]
find | finds element with specific key (public member function) [edit]
equal_range | returns range of elements matching a specific key (public member function) [edit]
lower_bound | returns an iterator to the first element not less than the given value (public member function) [edit]
upper_bound | returns an iterator to the first element greater than a certain value (public member function) [edit]
##### Observers
key_comp | returns the function that compares keys (public member function) [edit]
value_comp | returns the function that compares keys in objects of type value_type (public member function) [edit]

### [edit] Non-member functions

operator==operator!=operator<operator<=operator>operator>= | lexicographically compares the values in the map (function template) [edit]
std::swap(std::map) | specializes the std::swap algorithm (function template) [edit]

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