deque Class

Article
07/11/2012

The Standard Template Library (STL) sequence container deque arranges elements of a given type in a linear arrangement and, like vectors, allow fast random access to any element and efficient insertion and deletion at the back of the container. However, unlike a vector, the deque class also supports efficient insertion and deletion at the front of the container.

template < 
   class Type,  
   class Allocator=allocator<Type>  
> 
   class deque

Parameters

Type
The element data type to be stored in the deque.
Allocator
The type that represents the stored allocator object that encapsulates details about the deque's allocation and deallocation of memory. This argument is optional, and the default value is allocator<Type>.

Remarks

The choice of container type should be based in general on the type of searching and inserting required by the application. Vectors should be the preferred container for managing a sequence when random access to any element is at a premium and insertions or deletions of elements are only required at the end of a sequence. The performance of the list container is superior when efficient insertions and deletions (in constant time) at any location within the sequence is at a premium. Such operations in the middle of the sequence require element copies and assignments proportional to the number of elements in the sequence (linear time).

Deque reallocation occurs when a member function must insert or erase elements of the sequence:

If an element is inserted into an empty sequence, or if an element is erased to leave an empty sequence, then iterators earlier returned by begin and end become invalid.
If an element is inserted at the first position of the deque, then all iterators, but no references, that designate existing elements become invalid.
If an element is inserted at the end of the deque, then end and all iterators, but no references, that designate existing elements become invalid.
If an element is erased at the front of the deque, only that iterator and references to the erased element become invalid.
If the last element is erased from the end of the deque, only that iterator to the final element and references to the erased element become invalid.

Otherwise, inserting or erasing an element invalidates all iterators and references.

Constructors

deque

Constructs a deque. Several constructors are provided to set up the contents of the new deque in different ways: empty; loaded with a specified number of empty elements; contents moved or copied from another deque; contents copied or moved by using an iterator; and one element copied into the deque_Count times. Some of the constructors enable using a custom allocator to create elements.

Typedefs

allocator_type	A type that represents the allocator class for the deque object.
const_iterator	A type that provides a random-access iterator that can access and read elements in the deque as const
const_pointer	A type that provides a pointer to an element in a deque as a const.
const_reference	A type that provides a reference to an element in a deque for reading and other operations as a const.
const_reverse_iterator	A type that provides a random-access iterator that can access and read elements in the deque as const. The deque is viewed in reverse. For more information, see reverse_iterator Class
difference_type	A type that provides the difference between two random-access iterators that refer to elements in the same deque.
iterator	A type that provides a random-access iterator that can read or modify any element in a deque.
pointer	A type that provides a pointer to an element in a deque.
reference	A type that provides a reference to an element stored in a deque.
reverse_iterator	A type that provides a random-access iterator that can read or modify an element in a deque. The deque is viewed in reverse order.
size_type	A type that counts the number of elements in a deque.
value_type	A type that represents the data type stored in a deque.

Member Functions

assign	Erases elements from a deque and copies a new sequence of elements to the target deque.
at	Returns a reference to the element at a specified location in the deque.
back	Returns a reference to the last element of the deque.
begin	Returns a random-access iterator addressing the first element in the deque.
deque::cbegin	Returns a const iterator to the first element in the deque.
deque::cend	Returns a random-access const iterator that points just beyond the end of the deque.
clear	Erases all the elements of a deque.
deque::crbegin	Returns a random-access const iterator to the first element in a deque viewed in reverse order.
deque::crend	Returns a random-access const iterator to the first element in a deque viewed in reverse order.
deque::emplace	Inserts an element constructed in place into the deque at a specified position.
deque::emplace_back	Adds an element constructed in place to the end of the deque.
deque::emplace_front	Adds an element constructed in place to the start of the deque.
empty	Returns true if the deque contains zero elements, and false if it contains one or more elements.
end	Returns a random-access iterator that points just beyond the end of the deque.
erase	Removes an element or a range of elements in a deque from specified positions.
front	Returns a reference to the first element in a deque.
get_allocator	Returns a copy of the allocator object that is used to construct the deque.
insert	Inserts an element, several elements, or a range of elements into the deque at a specified position.
max_size	Returns the maximum possible length of the deque.
pop_back	Erases the element at the end of the deque.
pop_front	Erases the element at the start of the deque.
push_back	Adds an element to the end of the deque.
push_front	Adds an element to the start of the deque.
rbegin	Returns a random-access iterator to the first element in a reversed deque.
rend	Returns a random-access iterator that points just beyond the last element in a reversed deque.
resize	Specifies a new size for a deque.
deque::shrink_to_fit	Discards excess capacity.
size	Returns the number of elements in the deque.
swap	Exchanges the elements of two deques.

Operators

operator[]	Returns a reference to the deque element at a specified position.
deque::operator=	Replaces the elements of the deque with a copy of another deque.

Requirements

Header: <deque>

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deque Class

Parameters

Remarks

Constructors

Typedefs

Member Functions

Operators

Requirements

See Also

Reference

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