Visual Basic.NET How to Program (PDF)

Chapter 23 Data Structures and Collections 1137
Outline
23.1 Introduction
23.2 Self-Referential Classes
23.3 Linked Lists
23.4 Stacks
23.5 Queues
23.6 Trees
23.6.1 Binary Search Tree of Integer Values
23.6.2 Binary Search Tree of IComparable Objects
23.7 Collection Classes
23.7.1 Class Array
23.7.2 Class ArrayList
23.7.3 Class Stack
23.7.4 Class Hashtable
Summary Terminology Self-Review Exercises Answers to Self-Review Exercises Exercises
23.1 Introduction
The data structures that we have studied thus far, such as single-subscripted and doublesubscripted
arrays, have been of fixed sizes. This chapter introduces dynamic data structures,
which can grow and shrink at execution time. Linked lists are collections of data
items “lined up in a row”—users can make insertions and deletions anywhere in a linked
list. Stacks are important in compilers and operating systems; insertions and deletions are
made only at the stack’s top. Queues represent waiting lines; insertions are made only at
the back (also referred to as the tail) of a queue, and deletions are made only from the front
(also referred to as the head) of a queue. Binary trees facilitate high-speed searching and
sorting of data, efficient elimination of duplicate data items, representation of file-system
hierarchies and compilation of expressions into machine language. The various data structures
we just mentioned have many other interesting applications, as well.
In this chapter, we discuss each of the major types of data structures and then implement
programs that create and manipulate these data structures. We use classes, inheritance
and composition to create and package the data structures in ways that enhance reusability
and maintainability.
The chapter examples are practical programs that students will find useful in
advanced courses and in industrial applications. The programs devote special attention
to reference manipulation.
23.2 Self-Referential Classes
A self-referential class contains a reference member referring to a class object of the same
class type. For example, the class definition in Fig. 23.1 defines type CNode. This type has
two Private instance variables (lines 5–6)—Integer mData and CNode reference