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deque<T, Alloc>

Category: containers Component type: type

Description

A deque [1] is very much like a vector: like vector, it is a sequence that supports random access to elements, constant time insertion and removal of elements at the end of the sequence, and linear time insertion and removal of elements in the middle.

The main way in which deque differs from vector is that deque also supports constant time insertion and removal of elements at the beginning of the sequence [2]. Additionally, deque does not have any member functions analogous to vector's capacity() and reserve(), and does not provide any of the guarantees on iterator validity that are associated with those member functions. [3]

Example

deque<int> Q;
Q.push_back(3);
Q.push_front(1);
Q.insert(Q.begin() + 1, 2);
Q[2] = 0;
copy(Q.begin(), Q.end(), ostream_iterator<int>(cout, " "));
// The values that are printed are 1 2 0

Definition

Defined in the standard header deque, and in the nonstandard backward-compatibility header deque.h.

Template parameters

Parameter Description Default
T The deque's value type: the type of object that is stored in the deque.  
Alloc The deque's allocator, used for all internal memory management. alloc

Model of

Random access container, Front insertion sequence, Back insertion sequence.

Type requirements

None, except for those imposed by the requirements of Random access container, Front insertion sequence, and Back insertion sequence.

Public base classes

None.

Members

Member Where defined Description
value_type Container The type of object, T, stored in the deque.
pointer Container Pointer to T.
reference Container Reference to T
const_reference Container Const reference to T
size_type Container An unsigned integral type.
difference_type Container A signed integral type.
iterator Container Iterator used to iterate through a deque.
const_iterator Container Const iterator used to iterate through a deque.
reverse_iterator Reversible Container Iterator used to iterate backwards through a deque.
const_reverse_iterator Reversible Container Const iterator used to iterate backwards through a deque.
iterator begin() Container Returns an iterator pointing to the beginning of the deque.
iterator end() Container Returns an iterator pointing to the end of the deque.
const_iterator begin() const Container Returns a const_iterator pointing to the beginning of the deque.
const_iterator end() const Container Returns a const_iterator pointing to the end of the deque.
reverse_iterator rbegin() Reversible Container Returns a reverse_iterator pointing to the beginning of the reversed deque.
reverse_iterator rend() Reversible Container Returns a reverse_iterator pointing to the end of the reversed deque.
const_reverse_iterator rbegin() const Reversible Container Returns a const_reverse_iterator pointing to the beginning of the reversed deque.
const_reverse_iterator rend() const Reversible Container Returns a const_reverse_iterator pointing to the end of the reversed deque.
size_type size() const Container Returns the size of the deque.
size_type max_size() const Container Returns the largest possible size of the deque.
bool empty() const Container true if the deque's size is 0.
reference operator[](size_type n) Random Access Container Returns the n'th element.
const_reference operator[](size_type n) const Random Access Container Returns the n'th element.
deque() Container Creates an empty deque.
deque(size_type n) Sequence Creates a deque with n elements.
deque(size_type n, const T& t) Sequence Creates a deque with n copies of t.
deque(const deque&) Container The copy constructor.
template <class InputIterator>
deque(InputIterator f, InputIterator l)
[4]
Sequence Creates a deque with a copy of a range.
~deque() Container The destructor.
deque& operator=(const deque&) Container The assignment operator
reference front() Front Insertion Sequence Returns the first element.
const_reference front() const Front Insertion Sequence Returns the first element.
reference back() Back Insertion Sequence Returns the last element.
const_reference back() const Back Insertion Sequence Returns the last element.
void push_front(const T&) Front Insertion Sequence Inserts a new element at the beginning.
void push_back(const T&) Back Insertion Sequence Inserts a new element at the end.
void pop_front() Front Insertion Sequence Removes the first element.
void pop_back() Back Insertion Sequence Removes the last element.
void swap(deque&) Container Swaps the contents of two deques.
iterator insert(iterator pos, 
                const T& x)
Sequence Inserts x before pos.
template <class InputIterator>
void insert(iterator pos, 
            InputIterator f, InputIterator l)
[4]
Sequence Inserts the range [f, l) before pos.
void insert(iterator pos,
            size_type n, const T& x)
Sequence Inserts n copies of x before pos.
iterator erase(iterator pos) Sequence Erases the element at position pos.
iterator erase(iterator first, iterator last) Sequence Erases the range [first, last)
void clear() Sequence Erases all of the elements.
void resize(n, t = T()) Sequence Inserts or erases elements at the end such that the size becomes n.
bool operator==(const deque&, 
                const deque&)
Forward Container Tests two deques for equality. This is a global function, not a member function.
bool operator<(const deque&, 
               const deque&)
Forward Container Lexicographical comparison. This is a global function, not a member function.

New members

All of deque's members are defined in the Random access container, Front insertion sequence, and Back insertion sequence requirements. Deque does not introduce any new members.

Notes

[1] The name deque is pronounced "deck", and stands for "double-ended queue." Knuth (section 2.6) reports that the name was coined by E. J. Schweppe. See section 2.2.1 of Knuth for more information about deques. (D. E. Knuth, The Art of Computer Programming. Volume 1: Fundamental Algorithms, second edition. Addison-Wesley, 1973.)

[2] Inserting an element at the beginning or end of a deque takes amortized constant time. Inserting an element in the middle is linear in n, where n is the smaller of the number of elements from the insertion point to the beginning, and the number of elements from the insertion point to the end.

[3] The semantics of iterator invalidation for deque is as follows. Insert (including push_front and push_back) invalidates all iterators that refer to a deque. Erase in the middle of a deque invalidates all iterators that refer to the deque. Erase at the beginning or end of a deque (including pop_front and pop_back) invalidates an iterator only if it points to the erased element.

[4] This member function relies on member template functions, which at present (early 1998) are not supported by all compilers. If your compiler supports member templates, you can call this function with any type of input iterator. If your compiler does not yet support member templates, though, then the arguments must either be of type const value_type* or of type deque::const_iterator.

See also

vector, list, slist


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