23.3.3 Class template
deque
[deque]
23.3.3.1 Class template
deque
overview [deque.overview]
1
A
deque
is a sequence container that, like a
vector
(
23.3.6
), 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. As with vectors, storage management is handled automatically.

...

23.3.3.4 deque modifiers [deque.modifiers]

iterator insert(const_iterator position, const T& x);
...
void push_front(const T& x);
void push_front(T&& x);
void push_back(const T& x);
void push_back(T&& x);
...
3
Complexity:
The complexity is linear in the number of elements inserted plus the lesser of the distances
to the beginning and end of the deque. Inserting a single element either at the beginning or end of a
deque always takes constant time and causes a single call to a constructor of
T.

iterator erase(const_iterator position);
iterator erase(const_iterator first, const_iterator last);
...
Complexity:
The number of calls to the destructor is the same as the number of elements erased, but
the number of calls to the assignment operator is no more than the lesser of the number of elements
before the erased elements and the number of elements after the erased elements.