Describe the functionality of a deque.
A deque adds items at either or both ends, and remove items at either or both ends.
A deque adds items only to the top, but remove from either or both sides. Deque or Double Ended Queue is a generalized version of Queue data structure that allows insert and delete at both ends.
A deque adds items to one side and remove items from the other side.
A deque adds items to either or both sides, but only removes items from the top.