1. Brief Review of ADTs and Class Implementation
Chapter 4-8
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2. Contents ADT? (ch. 2) Classes (ch. 4)
List and its class implementation (ch. 6)
Stack and its class implementation (ch. 7)
Queue and its class implementation (ch. 8)
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3. Objectives Review ADTs Review classes in C++
Review list with class implementation
Review stack with class implementation
Review Queue with class implementation
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4. What is ADT? ADT = data items + operations on the data
Implementation of ADT
Storage/data structures to store the data
Algorithms for the operations, i.e., how to do it
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5. Structs and Classes Similarities
Essentially the same syntax
Both are used to model objects with multiple attributes (characteristics)
represented as data members
also called fields … or …
instance or attribute variables
Thus, both are used to process non-homogeneous data sets.
Nyhoff, ADTs, Data Structures and Problem Solving with C++, Second Edition, © 2005 Pearson Education, Inc. All rights reserved

6. Structs vs. Classes Differences
No classes in C
Members public by default
Can be specified private
Both structs and classes in C++
Structs can have members declared private
Class members are private by default
Can be specified public
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7. Advantages in C++ (structs and Classes)
C++ structs and classes model objects which have:
Attributes represented as data members
Operations represented as functions (or methods)
Leads to object oriented programming
Objects are self contained
"I can do it myself" mentality
They do not pass a parameter to an external function
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8. Class Declaration
Syntax class ClassName { public: Declarations of public members private: Declarations of private members };
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9. Designing a Class
Data members normally placed in private: section of a class (information hiding)
Function members usually in public: section (exported for external use)
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10. Class Libraries Class declarations placed in header file
Given .h extension
Contains data items and prototypes
Implementation file
Same prefix name as header file
Given .cpp extension
Programs which use this class library called client programs
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11. Translating a Library
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12. Example of User-Defined Time Class
Now we create a Time class (page 150)
Actions done to Time object, done by the object itself
Note interface for Time class object, Fig. 4.2
Data members private – inaccessible to users of the class
Information hiding
class Time {
private:
unsigned myHours, myMinutes;
char myAMorPM;
public: … };
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13. Constructors Understanding Constructors, p158-159
Initialize data members
Optional: allocate memory
Note constructor definition in Time.cpp example (p161)
Syntax ClassName::ClassName (parameter_list) : member_initializer_list { // body of constructor definition }
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14. Constructors myHours = 0; myMinutes = 0; myAMorPM = ‘A’; } Data member
Time::Time() {
myHours = 0;
myMinutes = 0;
myAMorPM = ‘A’; }
Time::Time(unsigned h, unsigned m, char c) :
myHours(h), myMinutes(m), myAMorPM(c) {
Data member
initialization
Nyhoff, ADTs, Data Structures and Problem Solving with C++, Second Edition, © 2005 Pearson Education, Inc. All rights reserved

15. Overloading Functions
Note existence of multiple functions with the same name Time(); Time(unsigned initHours, unsigned initMinutes, char initAMPM);
Known as overloading
Compiler compares numbers and types of arguments of overloaded functions
Checks the "signature" of the functions
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16. Default Arguments
Possible to specify default values for constructor arguments Time(unsigned initHours = 12, unsigned initMinutes = 0, char initAMPM = 'A');
Consider Time t1, t2(5), t3(5,30), t4(5,30,'P');
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17. Copy Operations(p166) During initialization Time t = bedTime
During Assignment t = midnight;
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18. Overloading Operators
Same symbol can be used more than one way
Operator , function: operator ()
Two cases
If  is a function member: a b  a.operator (b)
Otherwise, a b  operator (a,b)
Operators: +,-,*,/
Operators: <<, >>
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19. Overloading << Question: which one is right? Why? See p170-171
void operator<<(ostream& out, const Time& t)
ostream& operator<<(ostream& out, const Time& t)
See p
See example p173: why need a member function to overload << and >>?
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20. Friend Functions Note use of two functions used for output
display() and operator<<()
Possible to specify operator<<() as a "friend" function
Thus given "permission" to access private data elements
Declaration in .h file (inside the class declaration with friend keyword) friend ostream & operator<<( ostream & out, const Time & t)
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21. Friend Functions
Definition in .cpp file ostream & operator<<( ostream & out, const Time & t) { out << t.myHours<<":" <<(t.myMinutes< 10? "0": "") <<t.myMinutes << ' '<<t.myAMorPM<<".M."; return out; }
Note - a friend function not member function
not qualified with class name and ::
receives class object on which it operates as a parameter
Author prefers not to use friend function
Violates principle of information hiding
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22. Other Operations Advance Operation Relational Operators
Time object receives a number of hours and minutes
Advances itself by adding to myHours, myMinutes
Relational Operators
Time object compares itself with another
Determines if it is less than the other
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23. Redundant Declarations
Note use of #include "Time.h" in
Time.cpp
Client program
Causes "redeclaration" errors at compile time
Solution is to use conditional compilation
Use #ifndef and #define and #endif compiler directives
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24. Pointers to Class Objects
Possible to declare pointers to class objects Time * timePtr = &t;
Access with timePtr->getMilTime() or (*timePtr).getMilTime()
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25. The this Pointer Every class has a keyword, this
a pointer whose value is the address of the object
Value of *this would be the object itself
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26. Exercises
Implement a polynomial class in the form of ax+b, coefficients a and b are integers.
Constructor
Overload operator+
Overload operator<<, do not use friend function.
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27. Review for Last Class’s Example
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28. Example for class “ax+b”
//poly.h: header file
#include <iostream>
#ifndef _POLY_H // avoid redundant declarations #define _POLY_H class Poly { private: int m_ca; //coefficient a int m_cb; public: Poly(int a, int b) : m_ca(a), m_cb(b) { }; //constructor void display(ostream& out) const; //for operator << overloading Poly operator+(const Poly& po); //overloading +
}; //do not forget to put ; !!!!
ostream& operator<<(ostream& out, const Poly& po); //overloading <<
#endif
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29. Example: ax+b //poly.cpp: implementation file #include “poly.h”
using namespace std;
void Poly::display(ostream& out) const { out << m_ca << “x + ” << m_cb << endl; } Poly Poly::operator+(const Poly& po) { Poly c; c.m_ca = this->m_ca + po.m_ca; //what is “this”? Do we need it here? c.m_cb = m_cb + po.m_cb; return c; }
ostream& operator<<(ostream& out, const Poly& po) { po.display(out);
return out; }
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30. To-do-list Review: class, overloading operators In-class Exercise
Operator “-” and “>>” overloading in last class example
List implementations
Destructor
Copy constructor
Assignment operator
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31. Lists
Chapter 6
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32. Chapter Contents 6.1 List as an ADT
6.2 An Array-Based Implementation of Lists
6.3 An array Based Implementation of Lists with Dynamic Allocation
6.4 Introduction to Linked Lists
6.5 A Pointer-Based Implementation of Linked Lists in C++
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33. Chapter Objectives To study list as an ADT
Build a static-array-based implementation of lists and note strengths, weaknesses
Build a dynamic-array-based implementation of lists, noting strengths and weaknesses
See need for destructor, copy constructor, assignment methods
Take first look at linked lists, note strengths, weaknesses
Study pointer-based implementation of linked lists
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34. Consider Every Day Lists
Groceries to be purchased
Job to-do list
List of assignments for a course
Dean's list
Can you name some others??
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35. Properties of Lists Can have a single element
Can have no elements  empty!
There can be lists of lists
We will look at the list as an abstract data type
Homogeneous
Finite length
Sequential elements
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36. Basic Operations Construct an empty list
Determine whether or not empty
Insert an element into the list
Delete an element from the list
Traverse (iterate through) the list to
Modify
Output
Search for a specific value
Copy or save
Rearrange
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37. Designing a List Class
Should contain at least the following function members
Constructor
empty()
insert()
delete()
display()
Implementation involves
Defining data members
Defining function members from design phase
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38. Array-Based Implementation of Lists
An array is a viable choice for storing list elements
Element are sequential
It is a commonly available data type
Algorithm development is easy
Normally sequential orderings of list elements match with array elements
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39. typedef int ElementType; Class List { private:
const int CAPACITY = 1000;
typedef int ElementType;
Class List {
private:
int size; //# of elements
ElementType array[CAPACITY];
public: … };
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40. Implementing Operations
Constructor
Static array allocated at compile time. No need to allocate explicitly!
Empty
Check if size == 0
Traverse
Use a loop from 0th element to size – 1
Insert
Shift elements to right of insertion point
Delete
Shift elements back
Also adjust size up or down
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41. List Class with Static Array
Must deal with issue of declaration of CAPACITY, p262
Use typedef mechanism typedef Some_Specific_Type ElementType ElementType array[CAPACITY];
For specific implementation of our class we simply fill in desired type for Some_Specific_Type
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42. List Class with Static Array
Can put typedef declaration inside or outside of class
Inside: must specify List::ElementType for reference to the type outside the class
Outside: now able to use the template mechanism (this will be our choice)
Also specify the CAPACITY as a const
Also choose to declare outside class
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43. List Class Example, p262 Declaration file, Fig. 6.1A
Note use of typedef mechanism outside the class
This example good for a list of int
Definition, implementation Fig. 6.1B
Note considerable steps required for insert() and erase() functions
Program to test the class, Fig 6.1C
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44. List Class with Static Array - Problems
Stuck with "one size fits all"
Could be wasting space
Could run out of space
Better to have instantiation of specific list specify what the capacity should be
Thus we consider creating a List class with dynamically-allocated array
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45. Dynamic-Allocation for List Class
Changes required in data members
Eliminate const declaration for CAPACITY
Add data member to store capacity specified by client program
Change array data member to a pointer
Constructor requires considerable change
Little or no changes required for
empty()
display()
erase()
insert()
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46. typedef int ElementType; Class List { private:
int size; //# of elements
int capacity;
ElementType *array;
public:
List (int cap); };
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47. Dynamic-Allocation for List Class
Note data changes in Fig. 6.2A, List.h,p270
Note implementation file Fig. 6.2B, List.cpp
Changes to constructor
Addition of other functions to deal with dynamically allocated memory
Note testing of various features in Fig. 6.2C, the demo program
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48. Dynamic-Allocation for List Class
Now possible to specify different sized lists cin >> maxListSize; List aList1 (maxListSize); List aList2 (500);
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49. New Functions Needed Destructor
When class object goes out of scope the pointer to the dynamically allocated memory is reclaimed automatically
The dynamically allocated memory is not
The destructor reclaims dynamically allocated memory
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50. New Functions Needed
Copy Constructor – makes a "deep copy" of an object, p278
When argument passed as value parameter
When function returns a local object
When temporary storage of object needed
When object initialized by another in a declaration
If copy is not made, observe results (aliasing problem, "shallow" copy)
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51. Copy Constructor, p280
The parameter must be a reference parameter and should be a const reference parameter as well
If value parameter, infinite chain of function calls!!!
List(const List& org)
Work to be done
Allocate memory
Ensure deep copy by element-by-element copy
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52. New Functions Needed Assignment operator
Default assignment operator makes shallow copy
Can cause memory leak, previous dynamically-allocated memory has nothing pointing to it
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53. Assignment Operator Must be member function, a=b  a.operator=(b)
Return const reference to the object
const ClassName& operator=(const ClassName& right)
First check if self-assignment: otherwise having problem in “list1 = list1”;
Avoid memory leak by releasing previous allocated memory
Ensure deep copy
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54. Difference between Copy constructor and Assignment Operator
Function return value?
Self assignment check?
Memory leak?
Deep copy?
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55. Notes on Class Design
If a class allocates memory at run time using the new, then a it should provide …
A destructor
A copy constructor (by complier to make a copy)
An assignment operator (by programmer)
Note Fig. 6.3 which exercises constructors and destructor, p263
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56. Future Improvements to Our List Class
Problem 1: Array used has fixed capacity Solution:
If larger array needed during program execution
Allocate, copy smaller array to the new one
Problem 2: Class bound to one type at a time Solution:
Create multiple List classes with differing names
Use class template
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57. Recall Inefficiency of Array-Implemented List
insert() and erase() functions inefficient for dynamic lists
Those that change frequently
Those with many insertions and deletions
So …
We look for an alternative implementation.
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58. Linked List Fix: For the array-based implementation:
First element is at location 0
Successor of item at location i is at location i + 1
End is at location size – 1
Fix:
Remove requirement that list elements be stored in consecutive location.
But then need a "link" that connects each element to its successor
Linked Lists !!
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59. Linked List Linked list nodes contain
Data part – stores an element of the list
Next part – stores link/pointer to next element (when no next element, null value)
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60. Linked Lists Operations
Construction: first = null_value;
Empty: first == null_value?
Traverse
Initialize a variable ptr to point to first node
Process data where ptr points
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61. Linked Lists Operations
Traverse (ctd)
set ptr = ptr->next, process ptr->data
Continue until ptr == null
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62. Operations: Insertion
predptr
Insertion
To insert 20 after 17
Need address of item before point of insertion
predptr points to the node containing 17
Get a new node pointed to by newptr and store 20 in it
Set the next pointer of this new node equal to the next pointer in its predecessor, thus making it point to its successor.
Reset the next pointer of its predecessor to point to this new node 20
newptr
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63. Operations: Insertion
Note: insertion also works at end of list
pointer member of new node set to null
Insertion at the beginning of the list
predptr must be set to first
pointer member of newptr set to that value
first set to value of newptr
 Note: In all cases, no shifting of list elements is required !
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64. Operations: Deletion Delete node containing 22 from list.
predptr
ptr
To free space
Delete node containing 22 from list.
Suppose ptr points to the node to be deleted
predptr points to its predecessor (the 20)
Do a bypass operation:
Set the next pointer in the predecessor to point to the successor of the node to be deleted
Deallocate the node being deleted.
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65. Linked Lists - Advantages
Access any item as long as external link to first item maintained
Insert new item without shifting
Delete existing item without shifting
Can expand/contract as necessary
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66. Linked Lists - Disadvantages
Overhead of links:
used only internally, pure overhead
If dynamic, must provide
destructor
copy constructor
No longer have direct access to each element of the list
Many sorting algorithms need direct access
Binary search needs direct access
Access of nth item now less efficient
must go through first element, and then second, and then third, etc.
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67. Linked Lists - Disadvantages
List-processing algorithms that require fast access to each element cannot be done as efficiently with linked lists.
Consider adding an element at the end of the list
Array
Linked List
a[size++] = value;
Get a new node;
set data part = value
next part = null_value
If list is empty
Set first to point to new node.
Else
Traverse list to find last node
Set next part of last node to point to new node.
This is the inefficient part
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68. Using C++ Pointers and Classes
To Implement Nodes
class Node { public:
DataType data;
Node * next; };
Note: The definition of a Node is recursive
(or self-referential)
It uses the name Node in its definition
The next member is defined as a pointer to a Node
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69. Working with Nodes
Declaring pointers Node * ptr; or typedef Node * NodePointer; NodePointer ptr;
Allocate and deallocate ptr = new Node; delete ptr;
Access the data and next part of node (*ptr).data and (*ptr).next or ptr->data and ptr->next
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70. Working with Nodes Note data members are public
This class declaration will be placed inside another class declaration for List (private section), p296
The data members data and next of struct Node will be public inside the class
will accessible to the member and friend functions of List
will be private outside the class
class Node { public: DataType data; Node * next; };
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71. Class List
typedef int ElementType; class List { private: class Node { public: ElementType data; Node * next; }; typedef Node * NodePointer;
data is public inside class Node
class Node is private inside List
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72. Data Members for Linked-List Implementation
A linked list will be characterized by:
A pointer to the first node in the list.
Each node contains a pointer to the next node in the list
The last node contains a null pointer
As a variation first may
be a structure
also contain a count of the elements in the list
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73. Function Members for Linked-List Implementation
Constructor
Make first a null pointer and
set mySize to 0
Destructor
Nodes are dynamically allocated by new
Default destructor will not specify the delete
All the nodes from that point on would be "marooned memory"
A destructor must be explicitly implemented to do the delete
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74. Function Members for Linked-List Implementation
Shallow Copy
Copy constructor for deep copy
By default, when a copy is made of a List object, it only gets the head pointer
Copy constructor will make a new linked list of nodes to which copy will point
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75. Function Members for Linked-List Implementation
Assignment operator?
Deep copy
Avoid memory leak
Avoid self assignment
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76. Stack Design and Implement a Stack class 3 options Static array
Dynamic array
Linked list
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77. Stack.h typedef int DataType;
class Stack { public: Stack(); Stack(const Stack& org); void push(const DataType& v); void pop(); DataType top() const; ~Stack();
private: class Node { public: DataType data; Node* next; Node(DataType v, Node* p) : data(v), next(0) { } };
typedef Node* NodePtr; NodePtr myTop;
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78. Queue Design and Implement a Queue class 3 options Static array
Dynamic array
Linked list
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79. Queue.h typedef int DataType; class Queue { public: //constructor
//… member functions private: class Node { public: DataType data; Node* next; Node(DataType v, Node* p) : data(v), next(0) { } };
typedef Node* NodePtr; NodePtr myFront, myback;
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80. After-class Exercises
Can you implement linked list-based Stack and Queue classes?
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