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Data Structures and Algorithms
with Object-Oriented Design Patterns in Python |
In the preceding section we saw that a stack comprises a pile
of objects that can be accessed only at one end--the top.
In this section we examine a similar data structure called a
single-ended queue .
Whereas in a stack we add and remove elements at the same end of the pile,
in a single-ended queue we add elements at one end
and remove them from the other.
Since it is always the first item to be put into the queue
that is the first item to be removed,
a queue is a first-in, first-out
or FIFO data structure.
Figure 
illustrates the basic queue operations.
Figure: Basic queue operations.
Program defines the Queue class.
The abstract Queue class extends the abstract Container
class defined in Program .
Hence, it comprises all the methods inherited from Container
plus the methods,
enqueue and eequeue,
and the head property.
As we did with stacks,
we examine two queue implementations--an array-based one and a linked-list one.
Program: Abstract Queue class.
Copyright © 2003, 2004 by Bruno R. Preiss, P.Eng. All rights reserved.