Data Structures

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Data Structures

• Joe Komar

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Course objectives

• Describe what data structures and algorithms are
• Write Java code to do simple and complex sorting
• Write Java code to implement stacks and queues
• Write Java code to implement linked lists
• Write Java code to implement various types of
  trees
• Write Java code to implement hash tables and
  heaps
• Write Java code to implement graphs
• Describe when to use which types of data
  structures

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Data Structure

• An arrangement of data in a computers memory
  (sometimes on disk)
• Includes
• Linked lists
• Stacks
• Binary trees
• Hash tables
• Graphs
• Etc.

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Algorithms

• Manipulate the data in data structures in various
  ways
• Searching
• Sorting
• Inserting
• Deleting

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Why study data structures

• Programmers tools e.g. stacks, queues
• Real-world data storage needs
• Student records
• Inventory records
• Etc.
• Real-world modeling
• Queues, stacks
• Graphs routes between locations, printed
  circuit boards, etc.

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Overview of data structures

• Array basis of many other structures
• Stack last-in first-out processing
• Queue first-in first-out processing
• Linked list quick insertion and deletion
• Binary tree quick if balanced tree
• Red-black tree tree always balanced
• 2-3-4 tree start of disk storage
• Hash table very fast access if key is known\
• Heap fast access to largest item
• Graph models many real-world situations

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Some definitions

• Database all data to be dealt with in a
  particular situation (restricted definition)
• Record units into which a database is divided
• Field smallest logical unit
• Key unique identifier for a record
• Search key the particular key value youre
  looking for

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Object-Oriented Review

• Objects model of real world containing methods
  and variables (instance of a class)
• Classes blueprints for objects
• Creating objects the new operator in Java
  (also called instantiating an object)
• Invoking methods use object name, followed by
  the dot operator (.) followed by the method name
  along with parameters needed
• (See example program)

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Object-Oriented Review

• Constructors to create new objects
• Access modifiers public, private, protected
• Inheritance using a superclass to create a
  subclass (parent-child, base-derived)
• Polymorphism different methods are called at
  run time based on actual object calling
• Related by inheritance
• Implements an interface

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Java I/O Review
public static String getString() throws
IOException InputStreamReader isr
new InputStreamReader(System.in)
BufferedReader br new BufferedReader(isr)
String s br.readLine() return s
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Java I/O Review
public static char getChar() throws IOException
String s getString() return
s.charAt(0)
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Java I/O Review
public static int getInt() throws IOException
String s getString() return
Integer.parseInt(s)
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Java I/O Review
public static double getDouble() throws
IOException String s
getString() Double aDub
Double.valueOf(s) return
aDub.doubleValue()
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Java I/O Review (see Komars site, QMCS490,
Working with Files)
try FileReader f new
FileReader("ReadIt.java") BufferedReader
b new BufferedReader(f) String s
null do s b.readLine()
if (s ! null)
System.out.println(s) while (s !
null) catch (Exception e)
System.out.println("File Error")
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Summary

• Data structure is an organization of data
• Correct choice of data structure is critical
• Algorithm is a procedure to accomplish a task
• In Java an algorithm is typically a method
• Data structures are programmers tools, useful in
  storing real-world data, and in modeling the
  real-world
• Database, record, key, and search key are terms
  to remember