EE441 Data Structures (Fall 2001)

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EE441 Data Structures(Fall 2001)

• Cüneyt F. Bazlamaçci
• Department of Electrical Electronics
  Engineering
• Middle East Technical University
• cuneytb_at_metu.edu.tr
• www.eee.metu.edu.tr/cb

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Course Outline (Tentative)

• Introduction to OOP
• Abstract Data Types, Classes Objects
• Arrays
• Complexity of algorithms
• Stacks
• Queues
• Dynamic memory management
• Linked Lists
• Trees, B-Trees
• Sorting and Hashing Algorithms

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Administrative Details

• Instructor (Section IV) Cüneyt F. Bazlamaçci
• Office EA-406
• Email cuneytb_at_metu.edu.tr
• Course Web Follow http//www.eee.metu.edu.tr/cb/
  
• Office Hours Anytime!
• Attendance will be taken but it will not affect
  your grade! (thus, no sleeping in the CR, o/w
  youll be kindly invited to sleep outside.)

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Chapter IIntroduction to OOP
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Object-Orientation

• We perceive the world as a world of objects
• You look around and see a chair, a table, a
  person, and the objects are related in one way or
  another.
• The object-oriented technique tries to imitate
  the way we think
• A system developed by using the object-oriented
  technique can be seen as a system consisting of a
  number of objects which cooperate to solve a
  task.

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A Shift in Thinking ?

• A fundamental change in approach
• Structured programming reflects the way that
  computers process information (e.g. sequential
  execution, conditional branching and repetition).
  As such, a problem is tackled by decomposing it
  into a flow of operations, data is of secondary
  importance.
• we do not naturally think in this way ? dealing
  with complex problems is difficult and bugs may
  not be obvious
• OO approach attempts to find a methodology and
  language that reflect the way that people think
  about problems.
• In fact, it appears that people tend to think in
  terms of things not operations.
• In OO development we refer to these "things" as
  objects

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Structured vs. OO Programming
STRUCTURED PROGRAMMING
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Structured Programming

• Using function
• Function program is divided into modules
• Every module has its own data and function which
  can be called by other modules.

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A New Approach

• Software developers sought a new approach for
  developing software. One that would . . .
• Produce highly maintainable software, where
  changing one part of a program would not break
  the rest
• Produce reusable software, where similar
  programming tasks could share common elements,
  without having to reinvent the wheel
• Make it easier to tackle complex programming
  problems and reduce the chances of introducing
  bugs into programs.
• These ideas led to the development of
  object-oriented (OO) software development.

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OO Approach

• OO development starts by thinking about the
  problem, and not about the program that will
  implement the solution
• In the real world, "things" have characteristics
  and behavior.
• e.g. a car is a "thing" that has a make, model,
  registration number and can accelerate, steer,
  brake, change gear etc.
• When we think about the objects involved in the
  problem, we actually think about their
  characteristics (attributes) and behavior
• An object-oriented language will allow us to
  model these attributes and behaviors.
• We construct a solution to the problem from these
  objects

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OO Programming

• A design and programming technique
• Objects have both data and methods
• Objects of the same class have the same data
  elements and methods
• Objects send and receive messages to invoke
  actions
• Key idea in object-oriented programming
• The real world can be accurately described as a
  collection of objects that interact with each
  other
• Pure OO Languages Smalltalk, Eiffel, Actor, Java
• Hybrid OO Languages C, Object-Pascal

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Structured vs. OO Programming (Recap.)
STRUCTURED PROGRAMMING
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OO Programming
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Some OOP Terminology

• object - usually a person, place or thing (a
  noun)
• method - an action performed by an object (a
  verb)
• class - a category of similar objects (such as
  automobiles)
• Class does not hold any values of the objects
  attributes

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Example of an Object Class
Example (Automobile)

• Methods
• Define data items (specify manufacturers name,
  model, year, etc.)
• Change a data item (color, engine, etc.)
• Display data items
• Calculate cost
• etc.

• Attributes
• manufacturers name
• model name
• year made
• color
• number of doors
• size of engine
• etc.

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Examples of Objects

• What the objects are, will be determined by the
  problem domain
• In a banking application
• customers, accounts, sums of money etc.
• In a library application
• books, journals, CD-Roms, members, etc.
• In a network simulator
• network nodes, queues, links, data packets etc.

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Why OOP?

• Save development time (and cost) by reusing code
• once an object class is created it can be used in
  other applications
• Easier debugging
• classes can be tested independently
• reused objects have already been tested

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Design Principles of OOP

• Three main design principles of Object-Oriented
  Programming(OOP)
• Encapsulation
• Polymorphism
• Inheritance

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Encapsulation

• Encapsulation to design, produce, and describe
  software so that it can be easily used without
  knowing the details of how it works.
• Also known as data hiding
• Only objects function which perform parts of the
  objects behavior can modify information in the
  object.
• An analogy
• When you drive a car, you dont have to know the
  details of how many cylinders the engine has or
  how the gasoline and air are mixed and ignited.
• Instead you only have to know how to use the
  controls.

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Polymorphism

• Polymorphism the same word or phrase can mean
  different things in different contexts
• Analogy
• in English, bank can mean side of a river or a
  place to put money
• Function Overloading
• The operation of one function depends on the
  argument passed to it.
• Example Fly(), Fly(low), Fly(150)

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Inheritance

• Inheritance a way of organizing classes
• Term comes from inheritance of traits like eye
  color, hair color, and so on.
• Classes with properties in common can be grouped
  so that their common properties are only defined
  once.
• Superclass provides its attributes methods to
  the subclass(es).
• Subclass inherits all its superclass attributes
  methods besides having its own unique
  attributes methods.

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An Inheritance Hierarchy
Superclass
Vehicle
Subclasses
Automobile
Motorcycle
Bus
Sedan
Sports Car
School Bus
Luxury Bus