|
Data Structures and Algorithms
with Object-Oriented Design Patterns in Python |
Program 
defines the
dequeueTail and getTail methods
of the DequeAsArray class.
Program: DequeAsArray class dequeueTail and getTail methods.
The getTail method that returns the object found at the tail of the deque, having first checked to see that the deque is not empty. If the deque is empty, it raises a ContainerEmpty exception. Under normal circumstances, we expect that the deque will not be empty. Therefore, the normal running time of this method is O(1).
The DequeueTail method removes an object from the tail of the deque and returns that object. First, it checks that the deque is not empty and throws an exception when it is. If the deque is not empty, the method sets aside the object at the tail in the local variable result; it decreases the _tail instance attribute by one modulo the length of the array; adjusts the _count accordingly; and returns result. All this can be done in a constant amount of time so the running time of DequeueTail is a constant.
Copyright © 2003, 2004 by Bruno R. Preiss, P.Eng. All rights reserved.