A deque is a data structure consisting of a list of items, on which the following operations are possible:
push(x): Insert item x on the front end of the deque.
pop(): Remove the front item from the deque and return it.
inject(x): Insert item x on the rear end of the deque.
eject(): Remove the rear item from the deque and return it.
Write routines to support the deque that take O(1) time per operation.