Data Structures, Algorithms, & Applications in C++
Chapter 9, Exercise 9

(a)

The ADT is given below

ADT Deque
{
   instances
      ordered list of elements; one end is called the front;
      the other is the rear;
   operations:
      isEmpty(): Return true if deque is empty, return false otherwise;
      getLeftElement(): Return leftmost element of deque;
      getRightElement(): Return rightmost element of deque;
      putAtLeft(x): Add x to left end of deque;
      putAtRight(x): Add x to right end of deque;
      removeFromLeft(): Delete leftmost element from deque and return it;
      removeFromRight(): Delete rightmost element from deque and return it;
}