22 Containers library [containers]

22.3 Sequence containers [sequences]

22.3.8 Class template deque [deque] Overview [deque.overview]

A deque is a sequence container that supports random access iterators.
In addition, it supports constant time insert and erase operations at the beginning or the end; insert and erase in the middle take linear time.
That is, a deque is especially optimized for pushing and popping elements at the beginning and end.
Storage management is handled automatically.
A deque meets all of the requirements of a container, of a reversible container (given in tables in [container.requirements]), of a sequence container, including the optional sequence container requirements ([sequence.reqmts]), and of an allocator-aware container (Table 76).
Descriptions are provided here only for operations on deque that are not described in one of these tables or for operations where there is additional semantic information.
namespace std { template<class T, class Allocator = allocator<T>> class deque { public: // types using value_type = T; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = implementation-defined; // see [container.requirements] using difference_type = implementation-defined; // see [container.requirements] using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // [deque.cons], construct/copy/destroy deque() : deque(Allocator()) { } explicit deque(const Allocator&); explicit deque(size_type n, const Allocator& = Allocator()); deque(size_type n, const T& value, const Allocator& = Allocator()); template<class InputIterator> deque(InputIterator first, InputIterator last, const Allocator& = Allocator()); deque(const deque& x); deque(deque&&); deque(const deque&, const Allocator&); deque(deque&&, const Allocator&); deque(initializer_list<T>, const Allocator& = Allocator()); ~deque(); deque& operator=(const deque& x); deque& operator=(deque&& x) noexcept(allocator_traits<Allocator>::is_always_equal::value); deque& operator=(initializer_list<T>); template<class InputIterator> void assign(InputIterator first, InputIterator last); void assign(size_type n, const T& t); void assign(initializer_list<T>); allocator_type get_allocator() const noexcept; // iterators iterator begin() noexcept; const_iterator begin() const noexcept; iterator end() noexcept; const_iterator end() const noexcept; reverse_iterator rbegin() noexcept; const_reverse_iterator rbegin() const noexcept; reverse_iterator rend() noexcept; const_reverse_iterator rend() const noexcept; const_iterator cbegin() const noexcept; const_iterator cend() const noexcept; const_reverse_iterator crbegin() const noexcept; const_reverse_iterator crend() const noexcept; // [deque.capacity], capacity [[nodiscard]] bool empty() const noexcept; size_type size() const noexcept; size_type max_size() const noexcept; void resize(size_type sz); void resize(size_type sz, const T& c); void shrink_to_fit(); // element access reference operator[](size_type n); const_reference operator[](size_type n) const; reference at(size_type n); const_reference at(size_type n) const; reference front(); const_reference front() const; reference back(); const_reference back() const; // [deque.modifiers], modifiers template<class... Args> reference emplace_front(Args&&... args); template<class... Args> reference emplace_back(Args&&... args); template<class... Args> iterator emplace(const_iterator position, Args&&... args); void push_front(const T& x); void push_front(T&& x); void push_back(const T& x); void push_back(T&& x); iterator insert(const_iterator position, const T& x); iterator insert(const_iterator position, T&& x); iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> iterator insert(const_iterator position, InputIterator first, InputIterator last); iterator insert(const_iterator position, initializer_list<T>); void pop_front(); void pop_back(); iterator erase(const_iterator position); iterator erase(const_iterator first, const_iterator last); void swap(deque&) noexcept(allocator_traits<Allocator>::is_always_equal::value); void clear() noexcept; }; template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>> deque(InputIterator, InputIterator, Allocator = Allocator()) -> deque<iter-value-type<InputIterator>, Allocator>; // swap template<class T, class Allocator> void swap(deque<T, Allocator>& x, deque<T, Allocator>& y) noexcept(noexcept(x.swap(y))); }