Data Structures (INE2011)

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1 Data Structures (INE2011) Electronics and Communication Engineering Hanyang University Haewoon Nam ( hnam@hanyang.ac.kr ) Lecture 1 1

2 Data Structures Data? Songs in a smartphone Photos in a camera Files in a computer Books in a book store Products in a Walmart warehouse Characteristics of the data? Name, Owner, Date, Creator Color, Length(Size), Category Similar Items, Location, Misc 2

3 Data Structures Organizing data Arrangement Management Search Example: categorized by name Keywords Searching speed Sort Quick response 3

4 Data Structures Data structure A scheme for organizing data in the memory of a computer. Commonly used data structures Arrays Stacks Queues Lists Heaps Trees Graphs Binary Tree 4

5 Fundamental Principles of OOP Inheritance Inherit members from parent class Abstraction Define and execute abstract actions Encapsulation Hide the internals of a class Polymorphism Access a class through its parent interface 5

6 Inheritance Child classes inherits the characteristics of the parent class Attributes (fields and properties) Operations (methods) Child class can extend the parent class Add new fields and methods Redefine methods (modify existing behavior) Inheritance has a lot of benefits Extensibility Reusability Provides abstraction Eliminates redundant code 6

7 Inheritance Example Derived class Person +Name: String +Address: String Base class Derived class Employee +Company: String +Salary: double Student +School: String 7

8 Inheritance Specify the name of the base class after the name of the derived class public class Shape... public class Circle : Shape... In the constructor of the derived class we use the keyword base to invoke the constructor of the base class public Circle (int x, int y) : base(x)... 8

9 Inheritance Example class Employee public: Employee(string thename, float thepayrate); string getname(); float getpayrate(); float pay(float hoursworked); protected: string name; float payrate; ; Employee::Employee(string thename, float thepayrate) name = thename; payrate = thepayrate; string Employee::getName() return name; float Employee::getPayRate() return payrate; float Employee::pay(float hoursworked) return hoursworked * payrate; 9

10 Inheritance Example (no reuse) class Manager public: Manager(string thename, float thepayrate, bool issalaried); string getname(); float getpayrate(); bool getsalaried(); float pay(float hoursworked); protected: string name; float payrate; bool salaried; ; Manager::Manager(string thename, float thepayrate, bool issalaried) name = thename; payrate = thepayrate; salaried = issalaried; string Manager::getName() return name; float Manager::getPayRate() return payrate; bool Manager::getSalaried() return salaried; float Manager::pay(float hoursworked) if (salaried) return payrate; /* else */ return hoursworked * payrate; 10

11 Inheritance Example (with reuse) class Employee public: Employee(string thename, float thepayrate); string getname(); float getpayrate(); float pay(float hoursworked); protected: string name; float payrate; ; #include "employee.h" class Manager : public Employee public: Manager(string thename, float thepayrate, bool issalaried); bool getsalaried(); float pay(float hoursworked); protected: bool salaried; ; 11

Abstraction Abstraction is a way of generalization Ignoring irrelevant features, properties, or functions and emphasizing the relevant ones Abstraction = managing complexity Allows us to represent a

12 Abstraction Abstraction is a way of generalization Ignoring irrelevant features, properties, or functions and emphasizing the relevant ones Abstraction = managing complexity Allows us to represent a complex reality in terms of a simplified model Interfaces provide abstractions You only need to know how to use it You don t have to know the internal implementation Abstract the properties of the object to keep only what we need Looking at an object, we see those things that have meaning to us Abstraction highlights the properties of an entity that we need and hides the others 12

13 Abstraction Example int main( ) Adder a; a.addnum(10); a.addnum(20); a.addnum(30); cout << "Total " << a.gettotal() <<endl; return 0; #include <iostream> using namespace std; class Adder public: // constructor Adder(int i = 0) total = i; // interface to outside world void addnum(int number) total += number; // interface to outside world int gettotal() return total; ; private: // hidden data from outside world int total; ; 13

Encapsulation Encapsulation hides the implementation details No interface members should be hidden Benefits of encapsulation Ensures that structural changes remain local: Changing the class internals

14 Encapsulation Encapsulation hides the implementation details No interface members should be hidden Benefits of encapsulation Ensures that structural changes remain local: Changing the class internals does not affect any code outside of the class Changing methods' implementation does not reflect the clients using them Encapsulation allows adding some logic when accessing client's data E.g. validation on modifying a property value Hiding implementation details reduces complexity easier maintenance 14

15 Polymorphism Polymorphism = ability to take more than one form (objects have more than one type) A class can be used through its parent interface A child class may override some of the behaviors of the parent class Polymorphism allows abstract operations to be defined and used Abstract operations are defined in the base class' interface and implemented in the child classes Declared as abstract or virtual 15

16 Polymorphism Example Abstract class Figure +CalcSurface() : double Abstract action Concrete c lass Overriden action Square -x : int -y : int -size : int Circle -x : int -y : int -radius: int Overriden action override CalcSurface() return size * size; override CalcSurface() return PI * radius * raduis; 16

17 Polymorphism Example int main () Rectangle rect; Triangle trgl; Polygon * ppoly1 = &rect; Polygon * ppoly2 = &trgl; ppoly1->set_values (4,5); ppoly2->set_values (4,5); cout << rect.area() << '\n'; cout << trgl.area() << '\n'; return 0; #include <iostream> using namespace std; class Polygon protected: int width, height; public: void set_values (int a, int b) width=a; height=b; ; class Rectangle: public Polygon public: int area() return width*height; ; class Triangle: public Polygon public: int area() return width*height/2; ; 17

Chapter 1: Object-Oriented Programming Using C++

Chapter 1: Object-Oriented Programming Using C++ Objectives Looking ahead in this chapter, we ll consider: Abstract Data Types Encapsulation Inheritance Pointers Polymorphism Data Structures and Algorithms