CS1102C Bridging course

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CS1102C Bridging course

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Title: CS1102C Bridging course

1
CS1102C Bridging course

Kiruthika Ramanathan
Kiruthika_r_at_nus.edu.sg

2
Course outline
Date Venue Lesson
5th Dec/12th Dec LT6 Object Oriented Design
6th Dec/13th Dec LT6 Basic C
7th Dec/14th Dec LT6 Classes
7th Dec/14th Dec Cales PC Cluster Lab 1 Intro to OOP
8th Dec/ 15th Dec LT6 Inheritance and overloading
9th Dec/16th Dec LT6 Data structures a primer
9th Dec/16th Dec Cales PC Cluster Lab 2 Advanced OOP with C
3
Bridging course objectives

Understanding and implementation Object Oriented
Programming
Competent programming with C
Preparation for CS1102C with primer lectures on
data structures

4
Contents

Objected Oriented Design
Basic C
Classes
Inheritance
Operator overloading
Intro to Data Structures
1 Linked lists and stacks
2 Recursion and sorting
3 Binary Trees

5
Object oriented analysis
Object oriented analysis is based upon concepts
that we first learnt in kindergarten objects and
attributes, classes and members, wholes and
parts. Why it has taken us so long to apply these
concepts to the analysis and specification of
information systems is anyones guess perhaps
we have been too busy following the flow during
the heyday of structured analysis to consider the
alternatives ?
6
A short Intro

Objects Everything goes around them
Focus on defining the objects (a car for eg)
Characteristics
Manipulations
Behaviours
etc
Modular programming

7
A short Intro

Data modelling
Classes
Encapsulation
Inheritance

8
Why should I learn OOP

Even if u dont work now with OOP, one day you
will
More oop capabilities in Language
Java and C are common but there are more OOP
add ons to other langiages
OOP techniques in PERL is quite hot
VB.net is supposed to be fully Obj oriented
OOP does give an edge.

9
OOP definitions
Object Oriented Programming programs which are oriented around objects. Encapsulation, Polymorphism, and Inheritance increase code reuse and decrease code maintenance
Class Defines the variables the methods common to all objects of a certain kind.
Object An instance of a class. A class must be instantiated into an object before it can be used in the software.
Encapsulation The act of placing data and the operations that perform on that data in the same class. The class then becomes the 'capsule' or container for the data and operations.
10
OOP definitions
Inheritance Reuse of base classes (superclasses) to form derived classes (subclasses).
Coupling The degree of mutual interdependence between modules/components. Lower coupling gt more reusable methods. Keep coupling to a minimum but not zero
11
OOP Definitions
Visibility The ability to 'see' parts of an object from outside. Lower visibility is better.
Dependency The degree that one component relies on another to perform its responsibilities. Lower dependency is better.
12
Example 1

Objective System to draw figures
Objects The figures to be drawn (circle, square,
rectangle, triangle etc) gt circle object, square
object etc
Each object has an operation draw inside it
Method draw
c.draw() is a different method from s.draw().
Method draw is encapsulated in class

Encapsulation The act of placing data and the
operations that perform on that data in the same
class. The class then becomes the 'capsule' or
container for the data and operations.
13
Example 1 contd

Objective System to draw figures
With top down design

14
Functional vs Object decomposition
Functional decomposition emphasizes the
operations Object oriented decomposition
emphasizes the role of the objects c.draw()
versus draw(cir) OOP gives a cleaner
separation No ripple effect Eg If you want to
add a line to the list of figures to draw, then
Main() circle c, square s, line l c.draw() s.draw() l.draw() void draw(FIG) if FIGcircle draw a circle else if FIGline draw a line else end if
15
Exercise 1
Objective Implement a draw figure system and
take into consideration the input arguments, i.e,
circle radius, square length, rectangle length
and breadth. and returns the area and perimeter
of the figures. Come up with an OOP and top down
design pseudo codes. Hint To include variables
in a class you define the variables as you define
a method
16
Creating Objects

Abstraction Focus on the essential aspects

17
Creating Objects

Properties of a good abstraction
Well named
Name must reflect the nature of the abstraction
Coherence
Related attributes from the viewpoint of user
Accuracy
Object must not be supernatural to the domain
Minimal
Attributes of objects must be just what is
required.
Redundancy is not encouraged
Complete
Whatever is needed must be there

18
Exercise 2

Come up with some abstractions of Automobile
from the point of view of
Manufacturer
Owner
Are your abstractions
gt Well named, coherent, accurate, minimal, and
complete?

19
Seperation

Distinguish between goal and the means to achieve
User is interested in end product
Developer is interested in both the back end and
the front end
Need for seperation??

20
Seperation
The same implementation can be used for different
interface. Implementation is the union of
interface requirements
21
Exercise 3

Explain how separation is used in the following
cases
Telephone
Postal delivery serve
Stereo
Restaurant
How is separation used in
An operating system
A web browser
A compiler

22
Example 2 Furniture Class
Furniture chair, table chair.locationloc1 chair.
move(loc1,loc2) table.weight10 int table_weight
table_weightTable.weigh()
int furnitureweigh() return weight
23
Brief Intro to inheritance
Derived Class
Base Class
24
Brief Intro to inheritance
class sofas public furniture int
cushionNumber
class furniture int cost int
dimension int weight
include sofas.h" int main() sofas
cornerSofa cornerSofa.cost50
cornerSofa.cushionNumber2
Base Class
25
Advantages of OOP

Easier maintenance. Objects may be understood as
stand-alone entities
coupling a measure of module dependency
inter-module coupling minimized by keeping
message flow as low as possible
cohesion a degree of localization in a module
cohesion maximized by maintaining object details
(data functions) localized w.i. an object

26
Advantages of OOP
27
Advantages of OOP

Reusability Objects are reusable components
inheritance also enhances reusability
For some systems, there may be an obvious
mapping from real world entities to system
objects
Ability to tackle larger problem domains - handle
complexity by abstraction (data abstraction,
procedural abstraction, class abstraction)

28
Conclusion

Object Oriented Programming vs Top down design
OOP advantages
Some definitions
Abstraction and Separation
You should now be able to come up with some
simple OO designs

29
Your first OOP system

Consider a system that models the function of a
library. You can consider a virtual library, for
instance.
What objects would you find useful in an OO
design of this system?
What methods would you find useful in an OO
design of this system?
How would a top down design of this system work?

30
Contents

Objected Oriented Design
Basic C
Classes
Inheritance
Operator overloading
Intro to Data Structures
1 Linked lists and stacks
2 Recursion and sorting
3 Binary Trees

31
Basic C and VC

Some new operators and extensions in C
Construct a simple linked list program from start
to finish

32
Functions/Methods
int move (int startPoint, int Endpoint)
return distanceMoved //definition also serves
as declaration int main()
distancemove(start,end)
int move (int startPoint, int Endpoint) //
prototyping must be done in advance before the
function is called int main()
distancemove(start,end) int move (int
startPoint, int Endpoint) return
distanceMoved
33
Overloading Functions

Same names functions with different input
parameters

void print(int i) printf(First Overload
d\n, i) void print (int i, int j)
printf(Second Overload i i\n, i,j) int
main() print(7) print(7,10)
34
Did You realize?!?

Operators are overloaded!!

float float1, float2 sum1float1float2
int int1, int2 sum2int1int2
The operator for float1float2 is different
from the plus operator for int1int2 In fact, all
operators can be overloaded with a few
exceptions. We will discuss this further later in
the course
35
Exercise 1 Passing By reference
void move (point q) --q.x q.y int
main() point p int a5, b-12 p.xa p.y
b move(p) printf("xd, yd\n", p.x,
p.y)
struct point int x, y
What is the output??
36
New operators in C

Scope Resolution
Storage allocation new
Storage release delete/ delete

37
Scope Resolution

x External scope
clm Class scope
float x
void f(int n)
float x //local x (this is the auto value)
x1.5 //fs x
x2.5 //extern x

38
new and delete

Like malloc and free in c
new is used to allocate storage dynamically
Syntax
new followed by type
new int //allocates storage for 1 int
If allocation is not possible, then new int 0
int_ptrnew int
versus
int_ptr(int )malloc(sizeof(int))

39
new and delete

delete frees storage allocated by new.
Syntax
int_ptrnew int
delete int_ptr
OR
int_ptrnew int50
delete int_ptr
WARNING!!!!DONOT USE C storage management with
the C functions.
i.e, malloc delete is not good
nor is new free

40
Example of New and Delete Linked Lists

We are going to make a linked list of elephants.
Each elephant will have a name

41
So what is a linked list??

Each element keeps a pointer to the next element
on the list
struct elephant
char name50
elephant next

Each elephant has a element that points to the
next elephant
42
Visual of a linked list
43
The elephant list ?

Three functions
elephant get_elephants()
Returns the pointer to the first elephant
The first elephant points to the second elephant
and so on
print_elephants(elephant ptr)
void free_list(elephant ptr)
Frees the storage allocated to the elephants

44
Main function

int main()
elephant start
startget_elephants()
print_elephants(start)
free_list(start)
return EXIT_SUCCESS

45
Creating the elephants list

elephant get_elephants()
elephant currentnew elephant
elephant firstcurrent
int response
printf("\n\n\tName ")
scanf("s", current-gtname)
printf("\n\n\n\tAdd Another? (1yes, 0No))
")
scanf("d", response)

46
Creating the elephant list continued

while (response)
if((current-gtnextnew elephant)0)
printf("Out of memory")
return(first) //return whatever we have at
the moment
currentcurrent-gtnext
printf("\n\n\tName ")
scanf("s", current-gtname)
printf("\n\n\n\tAdd Another? (1yes, 0No))
")
scanf("d", response)
current-gtnext0
return(first)

47
Printing the elephants

void print_elephants(elephant ptr)
int count1
printf("\n\n\n")
while(ptr !0)
printf ("\nElephant number d is s",
count,ptr-gtname)
ptrptr-gtnext

48
Freeing the list

void free_list (elephant ptr)
elephant temp_ptr
while (ptr!0)
temp_ptrptr-gtnext
delete ptr
ptrtemp_ptr

49
C I/O

Include iostream.h
Use cin and cout to read and write to screen
Ex 1
float x
cin gtgt x
cout ltltx2
Ex 2
float x
cout ltlt'\n'
cin gtgt x
cout ltltx2 ltlt'\n'

streams vs stdio
50
const vs. define

define size 30
const int size30
include ltiostream.hgt
const int size30
main()
int size2size
size22
coutltltsize2 ltlt " "ltltsize ltlt'\n'
NOTE!! size will give an error!!

51
Conclusions

Some revision on C and introduction to some of
the C extensions
Functions and overloading
Passing by reference
, new, delete operators
Creating and manipulating linked lists
The cin and cout streams

52
Contents

Objected Oriented Design
Basic C
Classes
Inheritance
Operator overloading
Intro to Data Structures
1 Linked lists and stacks
2 Recursion and sorting
3 Binary Trees

53
Creating Classes

Syntax of classes is similar to the syntax of
structs
class testClass
int integer
float pseudo_real
struct testStruct
int integer
float psuedo_real

54
Classes continued

Class has several data members
Data members defined inside the class declaration
Methods can be defined inside the class
declaration.
A class only describes the storage required gt
does not allocate storage

55
Example of a class

class Win
int id
short x,y
short width, height
char visible
public
void moveWin(short, short)
char getName()
void minwin() width0
//Creating Objects
Win win1, win2, lots_of_wins100000

56
Example of a class continued

Win win1, win2, lots_of_wins100000
storage is allocated in accordance with the class
declaration
win1 has storage for int id, short data members
x, y, width, height etc
Three methodsgt moveWin, getName, and minWin
minWin is defined inside the declaration

57
Example of a class continued

moveWin is declared but not defined inside Win
To define moveWin elsewhere, use the scope
resolution operator
void WinmoveWin(short new_x, short new_y)
xnew_x
ynew_y
Scope resolution operator indicates that moveWin
belongs to the Win class.

58
Classes continued

By default, anything that is declared inside a
class are private
class Win
int id
short x,y
short width, height
char visible
public
void moveWin(short, short)
char getName()
void minwin() width0

private
public
59
Private vs Public

Private Data members and methods can only be
accessed by
Methods of the same class moveWin and getName
Friend functions (will be covered later)

60
Example Private vs Public

void f (Win w) //f is not a Win method
coutltltw.widthltltendl
//this is illegal since w.width is private.
w.minWin()
//this is legal since minWin has been declared
as a public method.

61
Class declarations styles and conventions
Typically place the data members together and the
methods together But this will still work

class C
float r //defaults to private
public
int m1() //public
float m2() //public
private
char c //private
public
void m3() //public
int z //public data member!!

62
Creating classes with struct keyword

struct Win_S
int id
short x,y
short width, height
char visible
void moveWin(short, short)
char getName()
void minwin() width0

63
Difference between class and struct

The final result is the same
NOTE
members are public by default when using struct
Members are private by default when using class.

64
Exercise 1

Write a declaration for class Employee that has
at least six data members and at least six
methods.
Write code slices that define Employee objects
and invoke each of the methods.

65
Example Stacks

Abstract data type
Zero or more elements
insertions and deletions occur at the same end gt
at the top
Create a Stack class with methods that allow the
user to
Push an element onto the stack
Pop an element off the stack
Print all the stack elements top to bottom

66
Stacks continued

Ensure stack integrity
Check that stack is not full before pushing
Check stack is not empty before popping
Information hiding
Stacks internal representation is made private
Encapsulation
Including methods within a stack

67
Intro to Enumeration

used to set up collections of named integer
constants.
define SPRING 0
define SUMMER 1
define FALL 2
define WINTER 3
OR
enum SPRING, SUMMER, FALL, WINTER
enum SPRING0, SUMMER1, FALL2, WINTER3

68
Stack Implementation

const int MaxStack10000
const char EmptyFlag'\0'
class Stack
enumFullStackMaxStack,EmptyStack-1
enumFalse0, True1
char itemsMaxStack
int top

public void dump_stack() int full() int
empty() char pop() void push(char) void
init()
69
Stack Implementation Continued

void Stackinit()
topEmptyStack //EmptyStack is -1
void Stackpush(char c)
if (full())
return
itemstopc

70
Stack Implementation Continued

char Stackpop()
if (empty())
return EmptyFlag //you cannot pop a stack if
it is empty
else
return itemstop--
int Stackempty()
if (topEmptyStack)
cerrltlt"Stack Empty"ltltendl
return True
else
return False

71
Stack Implementation Continued

int Stackfull()
if (top1FullStack)
cerrltlt"Stack full at"ltltFullStackltltendl
return True
else
return False
void Stackdump_stack()
for (int itop igt0 i--)
coutltltitemsiltltendl

72
Stack Implementation Continued

include "Stack.h"
include ltiostream.hgt
int main()
Stack s1
s1.init()
s1.push('a')
s1.push('b')
cout ltlts1.pop()ltltendl
s1.push('c')
cout ltlts1.pop()ltltendl
s1.push('d')
s1.push('e')

Output b c e d a
73
Constructors and Deconstructors

In the stack program we had to do
stack.init().
If the above is forgotten, then stack initializes
some junk value.
Constructors do automatic initialization
Programmer writes the constructor implementation
but does not call constructor

74
Stack constructor

void StackStack()
topEmptyStack
There is no need for the init() function.
In the main program do
Stack s1 //constructor is automatically invoked

75
More info about constructors

Default constructor takes in no arguments
Class can have more than one constructor
But the compiler and not the programmer invokes
the constructor
Constructor name is the same as the class name.
Constructors dont usually have a return value
Constructors MUST be public. WHY??

76
Overloaded constructors

class Color
float red
float green
float bluel
public
Color() //default constructor
Color(float, float, float) //parameterized

77
Constructor definitions

ColorColor()
red0.0
green0.0
blue0.0
ColorColor(float r, float g, float b)
redr greeng blueb

78
Calling different constructors

include Color.h
//always include the class headers
main
//using the default constructor
Color c1
//using the second constructor
Color c2(1.0, 0.5, 0.0)

79
Parameterized constructors with constants

ColorColor(float r, float g0.5, float b0.0)
redr greeng blueb
you can call this constructor with one or more
parameters
Color c2(1.0, 0.5, 0.0)
Color c3(1.0, 0.5) //b is initialized to 0.0

80
Constructors and dynamic storage

class ex1
char text
public
ex1()
ex1ex1()
textnew char20
strcpy(text, Hi world)
//call
ex1 example

81
Deconstructor

const long OneBillion1000000000
class BigStr
char string
long size
public
BigStr()
BigStr() //deconstructor

82
Deconstructors

BigStrBigStr()
string new charOneBillion1
for (long i0 iltOneBillion i)
stringi''
stringOneBillion'\0'
sizeOneBillion
BigStrBigStr()
delete string
cout ltlt "destructed string"ltltendl

83
Deconstructors

Free any storage the constructor allocates when
object is destroyed
Object can be destroyed by using delete operator
Or when object goes out of scope
Otherwise the storage becomes garbage.
Compiler does not provide a deconstructor if you
donot write one
Constructors and deconstructors donot return any
value.
How many deconstructors can a class have??

84
Constructors and deconstructors Example Zipcode

Objective
Create a class ZipC which manipulates Zip codes
of different lengths.
Zip code can be generated by either a integer or
a string.
Practice points
Information hiding the datamembers are private
Encapsulation include various methods in the
ZipC class
Revision on new and delete operators
Some new c operations and functions introduced

85
ZipCode main function

include "ZipC.h"
include ltstdlib.hgt
int main()
ZipC zip("60363-1312")
ZipC zip2(15124877)
ZipC zip3
zip.write()
zip2.write()
zip3.write()
return EXIT_SUCCESS

86
The ZipCode class ZipC

const int MinZip5
const int MaxZip32
const int InitChar'?'
include ltiostream.hgt
include ltstring.hgt
include ltstdio.hgt

class ZipC char code //private public Zip
C() ZipC(const char ) ZipC(const unsigned
long) ZipC() void write()
87
Constructor 1 default constructor

ZipCZipC()
codenew charMinZip1
for (int i0 iltMinZip i)
codeiInitChar
codei'\0'

88
Constructor 1 default constructor

Constructors set code to storage dynamically
using the new operator.
Default constructor allocated only MinZip1
Call using
ZipC zip1
(No arguments) so the default constructor is used

89
Conditional operator

The conditional operator (? ) is a ternary
operator (it takes three operands)
The first operand is implicitly converted to
bool. It is evaluated and all side effects are
completed before continuing.
If the first operand evaluates to true (1), the
second operand is evaluated.
If the first operand evaluates to false (0), the
third operand is evaluated.

90
Conditional operator continued

include ltiostream.hgt
int main()
int i 1, j 2
cout ltlt ( i gt j ? i j ) ltlt " is greater." ltlt
endl

91
Constructor 2string argument

ZipCZipC(const char zipstr)
int len len(strlen(zipstr)ltMaxZip)?strlen(zipst
r)MaxZip
codenew charlen1
strncpy(code, zipstr,len)
//copy first len chars of zipstr into code
codelen'\0'

92
Constructor 2string argument

Converts traditional c string to ZipC object.
Constructor only allocates the necessary space
using len.

93
Constructor 3 integer argument

ZipCZipC(const unsigned long zipnum)
char bufferMaxZip1
sprintf(buffer, "ld", zipnum)
codenew charstrlen(buffer)1
strcpy(code, buffer)

94
Constructor 3 integer argument

Use sprintf to convert the integer to null
terminated array of char.
Use a buffer with MaxZip storage to anable the
conversion.
Then allocate only the necessary number of char
cells.

95
deconstructor

ZipCZipC()
delete code

96
deconstructor

Deallocates whatever storage is given to
constructor.
If the bytes were not deallocated they will
become garbage ?
gt Program cannot access them.

97
Write function

void ZipCwrite()
coutltltcodeltltendl
//Note that code is defined as private in the
constructor. The main function cannot access it.

98
The output

int main()
ZipC zip("60363-1312")
ZipC zip2(15124877)
ZipC zip3
zip.write()
zip2.write()
zip3.write()
return EXIT_SUCCESS

99
Summary

Introduction to classes
Creating classes
Private vs public
Classes vs structs
Making a stack class
Constructors and deconstructors

100
Contents

Objected Oriented Design
Basic C
Classes
Inheritance
Operator overloading
Intro to Data Structures
1 Linked lists and stacks
2 Recursion and sorting
3 Binary Trees

101
Operator Overloading

2/3 (integer division)0
2.0/3.0 (floating point division)0.66667
Having the same / operator simplifies
manipulation
Sample application Complex number class

102
Operator overloading continued

class String
char string
public
String operator(const String)
String Stringoperator(const String s)
//code that defines the concatnation of two
strings

103
Operator overloading continued

class String
char string
public
int operatorgt(const String s)
int Stringoperatorgt(const String s)
return strcmp(string,s.string)gt0

104
Operator overloading continued

s1.stringlettuce
s2.stringlattice
if (s1gts2)
..

105
The class Complex

Implement complex numbers as an abstract data
type
Must support standard binary operations such as
addition and multiplication
Create complex with two double data members real
and imag

106
The class complex

class numComp
double real
double imag
public
void printcomp()
numComp operator(numComp c) //operator
numComp(double, double)
numComp(double)
numComp()

107
The complex operator

numComp numCompoperator (numComp c)
return numComp(realc.real,imagc.imag)
Overloading extends standard arithmetic operators
to Complex Numbers.

108
The complex operator

numComp numCompoperator (numComp c)
return numComp(realc.real,imagc.imag)
int main()
numComp c1(7.7, 5.5)
numComp c2(4.4, 3.3)
numComp c3
c3c1c2 //invokes the complex operators
c3.printcomp()

109
The complex operator

numComp numCompoperator (numComp c)
return numComp(realc.real,imagc.imag)
c1c2
You are calling c1 with c2 as argument.
Same as
c3c1.operator (c2)
c in the method refers to c2

110
Exercise

Overload the and / operators for the class
numComp

111
Friends

class eg1
char string
public
eg1(char S) //constructor
stringnew charstrlen(s)1
strcpy(string, s)
int main()
eg1 c1(hello)
int lenstrlen(c1.string) // THIS IS AN ERROR
WHY??

112
Friends

class eg1
char string // string is a private datamember
cannot be accessed from outside class eg1
public
eg1(char S) //constructor
stringnew charstrlen(s)1
strcpy(string, s)
int main()
eg1 c1(hello)
int lenstrlen(c1.string) //ERROR

113
Friends

class eg1
char string
eg1(char S) //constructor
stringnew charstrlen(s)1
strcpy(string, s)
friend int strlen(char ) // strlen is a friend
of eg1 class.
int main()
eg1 c1(hello)
int lenstrlen(c1.string) // Now there is no
problems ?

114
Example Complex Stack

Implement the stack class designed for complex
objects rather than chars
The method dump_stack() must access both the
complex class and the stack class
class ComplexStack
int top
Complex itemsmaxStack

115
Example Complex Stack

class Complex // because ComplexStack has
Complex items, make class complex visible to
class Complex stack
class ComplexStack
int top
Complex itemsmaxStack
public
..
friend void dump_stack(ComplexStack)

116
Example Complex Stack

class Complex
double real
double imag
public
friend void dump_stack(ComplexStack)

117
Example Complex Stack

void dump_stack(ComplexStack s)
for (int itop igt0 i--)
coutltlts.itemsi.realltlt ltlts.itemsi.imag
coutltltendl

118
Example Complex Stack

void dump_stack(ComplexStack s)
for (int itop igt0 i--)
coutltlts.itemsi.realltlt ltlts.itemsi.imag
//s is a stack item
coutltltendl

119
Example Complex Stack
Item5.real Item5.imag
TOP
Item5
Item4
Item3
Item2
Item1
Item0
s.items5.real
120
Friends continued

Dump_stack is a friend of complex stack and a
friend of complex
Use of friend functions
Allow a library function to access private
members of a class
Allow a function to access private members of two
or more classes

121
Friend classes

Friend Functions can be a method in a class OR a
toplevel method
class F
int adm
public
int f()
class ex1
int cdm
public
int m()
friend int t() //toplevel friend
friend int Ff()// fs friend method clarify
using the scope resolution

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Friend classes

If you want many methods of class F to access the
datamembers of class ex1, then you can make the
whole class a friend
class F
class C
friend F //Any method in F has full access to
methods in C

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Friend classes

class F
class C
friend F
F is a friend of class C
C is nota friend of F C can only access Fs
public info.
Symmetrical relationship has to be explicit
Not transitive gt if P is a friend of Q and Q is
a friend of R, P is not a friend of R unless it
is explicitly declared

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Assertions Program correctness

Condition that must be true at some particular
point in the programs execution
Id an assertion fails, the sytem detects and
reports the error.
Usually there are preconditions and
postconditions for a method.
Assertions are used in these cases

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AssertionExample Stack push and pop

void Stackpush(char c)
assert(!full()) //assert that the stack is not
full
itemstopc
assert(!empty())
INSTEAD OF
void Stackpush(char c)
if (full())
return
itemstopc

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Assertion contd

assert(!full())
Evaluates the expression !full().
If expression is true, execution proceeds
normally
If expression is false, program terminates.
The file assert.h must be included to implement
assertions

127
Method pop, asserted

char Stackpop()
char val
assert(!empty())
val itemstop--
assert(!full())
return val

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Summary

Operator Overloading
Friends
Assertions

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Contents

Objected Oriented Design
Basic C
Classes
Inheritance
Operator overloading
Intro to Data Structures
1 Linked lists and stacks
2 Recursion and sorting
3 Binary Trees

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Example A Binary Tree

Implement a binary search tree as a class
Each node contains a data
Data is arranged such that
For any node N, the data in the left subtree are
ltN
Data in the right subtree are gtN
Use BSTs to implement sorting and recursion
Revise the pertinent concepts so far.

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BST illustration
All the values in the left of a node are less
than or equal to the node value. All the values
on the right of the node are greater than the
node value
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Traversing a BST

InOrder
Preorder
PostOrder
When traversing a tree, a node can be visited 3
times
1st time Pre Order
2nd time In order
3rd Timr Post Order

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BST implementation

Two classes
Node
BST
BST is a friend to Node
Illustrate
Information hiding
All the data members are private
Encapsulation
Methods in BST and node

134
List versus tree implementation

class elephant
char name
elephant next
class node
char val
node lc //left child
node rc //right child

Points to next node
Points to two nodes, left and right
135
Class Node

const char None' '
class node
friend BST
char val
node lc //left child
node rc //right child
public
void write()
int empty()
node()

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Node method definitions

nodenode()
lc0
rc0
valNone //A node is always initialized with an
empty space
int nodeempty()
return valNone //1 if the node is empty, 0
otherwise
void nodewrite()
cout ltltval

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BST class

class BST
node root
node tree
void inorderAux(node)
void addNodeAux(const char v)
public
void inorder()
void addNode(const char)
BST()

138
BST methods

BSTBST()
roottreenew node
void BSTaddNode(const char v)
treeroot //start at the root always
addNodeAux(v)
void BSTinorder()
inorderAux(root)

139
BST methods contd

void BSTinorderAux(node n)
//if the current subtree is empty, it means
there are no nodes. So return.
if (n-gtempty())
return
inorderAux(n-gtlc) //traverse the left subtree
n-gtwrite() //visit and write the node
inorderAux(n-gtrc) //traverse the right subtree

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BST methods contd

void BSTaddNodeAux(const char v)
//if the root of the current subtree is empty,
store v there.
// And create a left and a right subtree
if (tree-gtempty())
tree-gtvalv
tree-gtlcnew node
tree-gtrcnew node
return
//otherwise, search either the left or the right
subtree to store the value
if (vlttree-gtval)
treetree-gtlc
else
treetree-gtrc
addNodeAux(v) //invokes itself

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Calling the BST

include "BST.h"
int main()
BST bst
bst.addNode('K')
bst.addNode('G')
bst.addNode('F')
bst.addNode.(R)
bst.addNode('I')
bst.addNode('H')
bst.inorder()

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Summary of the BST

Implement BST as a friend of node
All private members of node can be accessed by
BST
The node constructor initializes the node to
empty and makes sure there are no children
The nodewrite() writes the value of the node
The nodeempty() returns whether the node is
empty . This means there are no children

143
Summary of the BST continued

The BST constructor creates a new node and points
the root and the tree to it.
The node is initialized with the node constructor
Root always points to the root of the tree
(start) and the tree points to the current
subtree
Add node sets the tree to root
Allows search to start at the root of the entire
tree
addNodeAux stores the value, then creates a left
and right child
If the subtree is not empty, then set it to the
left or right and invokes itself.

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Summary of BST continued

Once the BST is created, inorder is used to
perform inorder traversal of tree
Recursive method
Traverses the nodes left subtree
Prints all the values
Traverses the nodes right subtrees

145
Visual BST
146
Design Exercise

Design an OO system to implement a BST of complex
numbers
You need to consider how to
Declare a complex object in a node
Compare two complex numbers when implementing
addNode (try operator overloading)
What classes will BST need to be a friend of?
What classes will node need to be a friend of?

147
Exercise

Implement the preorder traversal of the BST
In the preorder traversal, the BST visits the
node, prints a value and then moves to the left
node
i.e, the value is printed the first time the node
is visited.

148
Inheritance

Inheritance allows for code reusage.
Code written for one class can be used by other
classes in the heirarchy
If code is correct for a class, it is correct for
all inherited classes
Program is more robust

149
Basic concepts and syntax of inheritance

Base class, derived class
Consider class vehicle.
Every car is a vehicle
Car is a derived class from vehicle
Car is also a subclass of vehicle
Vehicle superclass/base class
Car subclass/ derived class

150
Direct and indirect inheritance

A car is a vehicle
A BMW is a car
BMW is a direct subclass of car
BMW is an indirect subclass of vehicle

151
Multiple inheritance

Car is a subclass of both vehicle and
expensiveToy gt one subclass, many superclass
Vehicle has two subclassesgt car and truck gt one
superclass, many subclass

152
Review of member accessibility

Datamembers and methods can be
Public global access
Private access by the class alone or by friends
Protected access by
Methods within the class
Methods within the class hierarchy (derived
classes)
Friend functions

153
Accessibility example

class pen
public
void set_pen(int a, int b)
void move_pen(int a, int b)
pen()
virtual pen()
protected
void initial_pen()
private
int x
int y

154
Accessibility continued

include "pen.h"
int main()
pen p
p.set_pen(0,0) //no problems ? this is a global
member
p.initial_pen() //error protected member
p.x0 //error private member

155
Deriving classes syntax

class B
.
class D access-specifier B
..

156
Access specifier

Either public, private or protected
Controls the access provided to the derived class
Defaults to private if omitted
Derived class CANNOT prohibit any inheritace
Derived class can specify additional data members
or methods.

157
Inheritance and access specifiers contd

Class Vehicle
public
float mph
float cost
float weight
Class Car public vehicle
Public
char brand_name100

158
Inheritance and access specifiers contd
Inherited from vehicle
Local to car
159
Inheritance and access specifiers contd

Public derivations
public member in base class is public in derived
class
protected member in base class is protected in
derived class
Private member in base class is private in base
class visible only in base class.

160
Public derivations

class B
public
int x
protected
int w
private
int z
class D public B
public
int y
void set_w(int a) wa

161
Public derivations
member Access Status in D How obtained
X Public From class B
W Protected From class B
Z Not Accessible From class B
Y Public Added by class D
set_w public Added by class D
162
Public derivations

int main()
D d1
d1.x33 //no problem x is public in B
d1.y99 //no problem y is public in D
d1.w77 //ERROR w is protected in B and D
d1.z88 // ERROR z is private

163
Inheritance and access specifiers contd

Protected derivations
Public member is protected
Protected member is protected
Private member is private in the base class, and
cannot be acessed

164
Public derivations

class B
public
int x
protected
int w
private
int z
class D protected B
public
int y

165
Protected derivations
member Access Status in D How obtained
X Protected From class B
W Protected From class B
Z Not Accessible From class B
Y Public Added by class D
166
Inheritance and access specifiers contd

Private derivations
Public member is private in derived class
Protected member is private in derived class
Private member is private in the base class, and
cannot be acessed
Derivation is private by default

167
Public derivations

class B
public
int x
protected
int w
private
int z
class D private B
public
int y

168
Private derivations
member Access Status in D How obtained
X Private From class B
W private From class B
Z Not Accessible From class B
Y Public Added by class D
169
Indirect inheritance

class Animal
protected
char species100
float lifeExpectancy
int warmBlooded

class Cat public Animal protected float
favPrey Class houseCat public Cat char
toys10 char catDoctor50 char owner50
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Indirect inheritance

class Animal
protected
char species100
float lifeExpectancy
int warmBlooded

class Cat public Animal protected float
favPrey Class houseCat public Cat char
toys10 char catDoctor50 char owner50
Animal 3 members Cat 4 members houseCat 7
members 3 added 1 direct inheritance
3 indirect inheritance
171
Access declarations