std::list
template < class T, class Alloc = allocator
List
Lists are sequence containers that allow constant time insert and erase operations anywhere within the sequence, and iteration in both directions.
List containers are implemented as doubly-linked lists; Doubly linked lists can store each of the elements they contain in different and unrelated storage locations. The ordering is kept internally by the association to each element of a link to the element preceding it and a link to the element following it.
They are very similar to forward_list: The main difference being that forward_list objects are single-linked lists, and thus they can only be iterated forwards, in exchange for being somewhat smaller and more efficient.
Compared to other base standard sequence containers (array, vector and deque), lists perform generally better in inserting, extracting(提取) and moving elements in any position within the container for which an iterator has already been obtained, and therefore also in algorithms that make intensive use of these, like sorting algorithms.
The main drawback(缺点) of lists and forward_lists compared to these other sequence containers is that they lack direct access to the elements by their position; For example, to access the sixth element in a list, one has to iterate from a known position (like the beginning or the end) to that position, which takes linear time in the distance between these. They also consume some extra memory to keep the linking information associated to each element (which may be an important factor for large lists of small-sized elements).
Container properties
- Sequence: Elements in sequence containers are ordered in a strict linear sequence. Individual elements are accessed by their position in this sequence.
- Doubly-linked list: Each element keeps information on how to locate the next and the previous elements, allowing constant time insert and erase operations before or after a specific element (even of entire ranges), but no direct random access.
- Allocator-aware: The container uses an allocator object to dynamically handle its storage needs.
Template parameters
- T: Type of the elements. Aliased as member type list::value_type.
- Alloc: Type of the allocator object used to define the storage allocation model. By default, the allocator class template is used, which defines the simplest memory allocation model and is value-independent. Aliased as member type list::allocator_type.
Member types
| member type | definition | notes |
|---|---|---|
| value_type | The first template parameter (T) | |
| allocator_type | The second template parameter (Alloc) | defaults to: allocator<value_type> |
| reference | allocator_type::reference | for the default allocator: value_type& |
| const_reference | allocator_type::const_reference | for the default allocator: const value_type& |
| pointer | allocator_type::pointer | for the default allocator: value_type* |
| const_pointer | allocator_type::const_pointer | for the default allocator: const value_type* |
| iterator | a bidirectional iterator to value_type | convertible to const_iterator |
| const_iterator | a bidirectional iterator to const value_type | |
| reverse_iterator | reverse_iterator |
|
| const_reverse_iterator | reverse_iterator<const_iterator> | |
| difference_type | a signed integral type, identical to: iterator_traits |
usually the same as ptrdiff_t |
| size_type | an unsigned integral type that can represent any non-negative value of difference_type | usually the same as size_t |
Member functions
- (constructor): Construct list (public member function )
- (destructor): List destructor (public member function )
- operator=: Assign content (public member function )
Iterators:
- begin: Return iterator to beginning (public member function )
- end: Return iterator to end (public member function )
- rbegin: Return reverse iterator to reverse beginning (public member function )
- rend: Return reverse iterator to reverse end (public member function )
- cbegin: Return const_iterator to beginning (public member function )
- cend: Return const_iterator to end (public member function )
- crbegin: Return const_reverse_iterator to reverse beginning (public member function )
- crend: Return const_reverse_iterator to reverse end (public member function )
Capacity:
- empty: Test whether container is empty (public member function )
- size: Return size (public member function )
- max_size: Return maximum size (public member function )
Element access:
- front: Access first element (public member function )
- back: Access last element (public member function )
Modifiers:
- assign: Assign new content to container (public member function )
- emplace_front:Construct and insert element at beginning (public member function )
- push_front: Insert element at beginning (public member function )
- pop_front: Delete first element (public member function )
- emplace_back: Construct and insert element at the end (public member function )
- push_back: Add element at the end (public member function )
- pop_back: Delete last element (public member function )
- emplace: Construct and insert element (public member function )
- insert: Insert elements (public member function )
- erase: Erase elements (public member function )
- swap: Swap content (public member function )
- resize: Change size (public member function )
- clear: Clear content (public member function )
Operations:
- splice: Transfer elements from list to list (public member function )
- remove: Remove elements with specific value (public member function )
- remove_if: Remove elements fulfilling condition (public member function template )
- unique: Remove duplicate values (public member function )
- merge: Merge sorted lists (public member function )
- sort: Sort elements in container (public member function )
- reverse: Reverse the order of elements (public member function )
Observers:
- get_allocator: Get allocator (public member function )
Non-member function overloads
- relational operators (list): Relational operators for list (function )
- swap (list): Exchanges the contents of two lists (function template )