[cs23021] on indexing in deque

[Mikhail Nesterenko]

IOOP students,

indexing ([] operator) is allowed for deque. Double-ended queue
(deque) is a standard template library (STL) container that
efficiently implements additions from back and front and indexing.
Similar to vector (and unlike "list" container), the operations of
adding and deleting elements from the middle are expensive.

thanks,
--
Mikhail