1. Chapter 4
ADT Sorted List

2. Lecture 9

3. Object-Oriented Design Methodology
Four stages to the decomposition process
Brainstorming
Filtering
Scenarios
Responsibility algorithms 3

4. Brainstorming
A group problem-solving technique that involves the spontaneous contribution of ideas from all members of the group
All ideas are potential good ideas
Think fast and furiously first, and ponder later
A little humor can be a powerful force
Brainstorming is designed to produce a list of candidate classes 4

5. Brainstorming
Step 1: review brainstorming principles at the beginning of the meeting
remind everyone that this is a group activity and personal style should be put aside.
Step 2: state specific session objectives
such as: “Today we want to come up with a list of candidate classes for the sorted ADT or grocery store checkout system.”
Step 3: use a round-robin technique to allow the group to proceed at an even tempo but give people enough time to think.
Each person should contribute a possible object class to the list.
A facilitator should keep the discussion on target, and a scribe should take notes. 5

6. Filtering Determine which are the core classes in the problem solution
Build CRC cards for final classes
There may be two classes in the list that have many common attributes and behaviors
There may be classes that really don’t belong in the problem solution 6

7. Scenarios
a sequence of steps that describes an interaction between a client/user and an application/program
Simulate class interactions
to Assign responsibilities to each class
Ask “What if?” questions
There are two types of responsibilities
What a class must know about itself (knowledge)
What a class must be able to do (behavior) 7

8. Responsibility Algorithms
The algorithms must be written for the responsibilities
Knowledge responsibilities usually just return the contents of one of an object’s variables
Action responsibilities are a little more complicated, often involving calculations 8

9. Computer Example
Let’s repeat the problem-solving process for creating an address list
Brainstorming and filtering
Circling the nouns and underlining the verbs
Create an address list that includes each person’s name, address, phone number and address. This list should then be printed in alphabetical order. The names to be included in the list are on scraps of paper and business cards. 9

10. Computer Example
First pass at a list of classes 10

11. Computer Example
Filtered list 11

12. CRC Cards 12

13. Responsibility Algorithms13

14. Object-oriented vs. Top Down
Object-oriented design
focuses on the data objects that are to be transformed
resulting in a hierarchy of objects
nouns are the primary focus
nouns in objects; verbs become operations
Top-down design
focus on the process of transforming the input into the output,
resulting in a hierarchy of tasks
verbs are the primary focus 14

15. Sorted Type Class Interface Diagram
MakeEmpty
Private data:
length
info [ 0 ]
[ 1 ]
[ 2 ]
[MAX_ITEMS-1]
currentPos
IsFull
GetLength
GetItem
PutItem
DeleteItem
ResetList
GetNextItem 15

16. Member functions
Which member function specifications and implementations must change to ensure that any instance of the Sorted List ADT remains sorted at all times?
PutItem
DeleteItem 16

17. InsertItem algorithm for SortedList ADT
Find proper location for the new element in the sorted list.
Create space for the new element by moving down all the list elements that will follow it.
Put the new element in the list.
Increment length. 17

18. Implementing SortedType member function PutItem
// IMPLEMENTATION FILE (sorted.cpp)
#include “itemtype.h” // also must appear in client code
void SortedType :: PutItem ( ItemType item )
// Pre: List has been initialized. List is not full.
// item is not in list.
// List is sorted by key member using function ComparedTo.
// Post: item is in the list. List is still sorted. { . } 18

19. void SortedType :: PutItem ( ItemType item )
{ bool moreToSearch;
int location = 0;
// find proper location for new element
moreToSearch = ( location < length );
while ( moreToSearch )
{ switch ( item.ComparedTo( info[location] ) )
{ case LESS : moreToSearch = false;
break;
case GREATER : location++; }
} // make room for new element in sorted list
for ( int index = length ; index > location ; index-- )
info [ index ] = info [ index - 1 ];
info [ location ] = item;
length++; 19

20. DeleteItem algorithm for SortedList ADT
Find the location of the element to be deleted from the sorted list.
Eliminate space occupied by the item by moving up all the list elements that follow it.
Decrement length. 20

21. Implementing SortedType member function DeleteItem
// IMPLEMENTATION FILE continued (sorted.cpp)
void SortedType :: DeleteItem ( ItemType item )
// Pre: List has been initialized.
// Key member of item is initialized.
// Exactly one element in list has a key matching item’s key.
// List is sorted by key member using function ComparedTo.
// Post: No item in list has key matching item’s key.
// List is still sorted. { . } 21

22. void SortedType :: DeleteItem ( ItemType item ){
int location = 0;
// find location of element to be deleted
while ( item.ComparedTo ( info[location] ) != EQUAL )
location++;
// move up elements that follow deleted item in sorted list
for ( int index = location + 1 ; index < length; index++ )
info [ index - 1 ] = info [ index ];
length--; } 22

23. Lecture 10

24. Improving member function GetItem
Recall that with the Unsorted List ADT
we examined each list element beginning
with info[ 0 ], until we either found a
matching key, or we had examined all
the elements in the Unsorted List.
How can the searching algorithm be improved for Sorted List ADT? 24

25. Retrieving Eliot from a Sorted List
length
info [ 0 ] Asad
[ 1 ] Bradley
[ 2 ] Henry
[ 3 ] Maxwell .
[MAX_ITEMS-1]
The sequential search
for Eliot can stop
when Henry has been
examined.
Why? 25

26. Binary Seach in a Sorted List
Examines the element in the middle of the array.
Is it the sought item?
If so, stop searching.
Is the middle element too small?
Then start looking in second half of array.
Is the middle element too large?
Then begin looking in first half of the array.
Repeat the process in the half of the list that should be examined next.
Stop when item is found, or when there is nowhere else to look and item has not been found. 26

27. 27 ItemType SortedType::GetItem ( ItemType item, bool& found )
// Pre: Key member of item is initialized.
// Post: If found, item’s key matches an element’s key in the list
// and a copy of that element is returned; otherwise,
// original item is returned.
{ int midPoint;
int first = 0;
int last = length - 1;
bool moreToSearch = ( first <= last );
found = false;
while ( moreToSearch && !found )
{ midPoint = ( first + last ) / 2 ; // INDEX OF MIDDLE ELEMENT
switch ( item.ComparedTo( info [ midPoint ] ) ) {
case LESS : // LOOK IN FIRST HALF NEXT
case GREATER : // LOOK IN SECOND HALF NEXT
case EQUAL : // ITEM HAS BEEN FOUND } 27

28. Trace of Binary Search
item = 45
info[0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
first midPoint last
LESS last = midPoint - 1
info[0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
first midPoint last
GREATER first = midPoint + 1 28

29. Trace continued
item = 45
info[0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
first, last
midPoint
GREATER first = midPoint + 1
info[0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
first,
midPoint,
last
LESS last = midPoint - 1 29

30. Trace concludes
item = 45
info[0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
last first
first > last found = false 30

31. 31 ItemType SortedType::GetItem ( ItemType item, bool& found )
// ASSUMES info ARRAY SORTED IN ASCENDING ORDER
{ int midPoint;
int first = 0;
int last = length - 1;
bool moreToSearch = ( first <= last );
found = false;
while ( moreToSearch && !found )
{ midPoint = ( first + last ) / 2 ;
switch ( item.ComparedTo( info [ midPoint ] ) )
{ case LESS : last = midPoint - 1;
moreToSearch = ( first <= last );
break;
case GREATER : first = midPoint + 1;
case EQUAL : found = true ;
item = info[ midPoint ]; }
}return item; 31

32. Allocation of memory
STATIC
ALLOCATION
Static allocation is the allocation of memory space at compile time.
DYNAMIC
ALLOCATION
Dynamic allocation is the allocation of memory space at run time by using operator new. 32

33. 3 Kinds of Program Data
STATIC DATA: memory allocation exists throughout execution of program.
static long SeedValue;
AUTOMATIC DATA: automatically created at function entry, resides in activation frame of the function, and is destroyed when returning from function.
DYNAMIC DATA: explicitly allocated and deallocated during program execution by C++ instructions written by programmer using unary operators new and delete 33

34. Arrays created at run time
If memory is available in an area called the free store (or heap), operator new allocates memory for the object or array and returns the address of (pointer to) the memory allocated.
Otherwise, the NULL pointer 0 is returned.
The dynamically allocated object exists until the delete operator destroys it. 34

35. Dynamic Array Allocation
char *ptr; // ptr is a pointer variable that
// can hold the address of a char
ptr = new char[ 5 ];
// dynamically, during run time, allocates
// memory for 5 characters and places into // the contents of ptr their beginning address
6000
6000
ptr 35

36. Dynamic Array Allocation
char *ptr ;
ptr = new char[ 5 ];
strcpy( ptr, “Bye” );
ptr[ 1 ] = ‘u’; // a pointer can be subscripted
std::cout << ptr[ 2] ;
6000
‘u’
6000
‘B’ ‘y’ ‘e’ ‘\0’
ptr 36

37. class SortedType<char>
Private data:
length
listData
currentPos ?
MakeEmpty
~SortedType
‘C’ ‘L’ ‘X’
RetrieveItem
InsertItem
DeleteItem .
GetNextItem 37 37

38. InsertItem algorithm for Sorted Linked List
Find proper position for the new element in the sorted list using two pointers predLoc and location, where predLoc trails behind location.
Obtain a node for insertion and place item in it.
Insert the node by adjusting pointers.
Increment length. 38

39. The Inchworm Effect 39

40. Inserting ‘S’ into a Sorted List
predLoc location
Private data:
length
listData
currentPos ?
‘C’ ‘L’ ‘X’
moreToSearch 40

41. Finding proper position for ‘S’
predLoc location
NULL
Private data:
length
listData
currentPos ?
‘C’ ‘L’ ‘X’
moreToSearch true 41

42. Finding proper position for ‘S’
predLoc location
Private data:
length
listData
currentPos ?
‘C’ ‘L’ ‘X’
moreToSearch true 42

43. Finding Proper Position for ‘S’
predLoc location
Private data:
length
listData
currentPos ?
‘C’ ‘L’ ‘X’
moreToSearch false 43

44. Inserting ‘S’ into Proper Position
predLoc location
Private data:
length
listData
currentPos
‘C’ ‘L’ ‘X’
‘S’
moreToSearch false 44

45. Why is a destructor needed?
When a local list variable goes out of scope, the memory space for data member listPtr is deallocated.
But the nodes to which listPtr points are not deallocated.
A class destructor is used to deallocate the dynamic memory pointed to by the data member. 45 45

46. Implementing the Destructor
SortedType::~SortedType()
// Post: List is empty; all items have
// been deallocated. {
NodeType* tempPtr;
while (listData != NULL)
tempPtr = listData;
listData = listData->next;
delete tempPtr; } 46

47. How do the SortedList implementations compare?47

48. SortedList implementations comparison48

49. List implementations comparison

50. Overview

51. Overview
In the object-oriented design of an airline passenger reservation program, suppose that "airplane" has been identified as one object and "airplane seat" has been identified as another object.
Focusing specifically on the airplane object, how does it relate to the airplane seat object?
A. a has-a relationship
B. an is-a relationship
C. an independent and equal relationship
D. a and b above
E. none of the above
Now, suppose that "airplane seat," "aisle seat," and "window seat" have been identified as objects.
Focusing specifically on the aisle seat object, how does it relate to the airplane seat object?

52. Overview design method’s focus on
In which stage of the object-oriented methodology,
the initial list of classes developed
the list of classes refined
"what if" questions asked
the algorithms developed
design method’s focus on
the process of transforming the input into the output,
resulting in a hierarchy of tasks
the data objects that are to be transformed,
resulting in a hierarchy of objects
brainstorming
filtering
scenarios
responsibility algorithms
Top-down
Object-oriented

53. Overview
Inserting into an unsorted list and inserting into a sorted list are the same time complexity.
In a sorted list, there is a semantic relationship between successive items in the list.
Deleting from a sorted array based list requires that the elements below the one being deleted be moved up one slot.
Searching an unsorted list and a sorted list are always the same time complexity.
You can perform a binary search on both a linked and an array-based implementation of a sorted list.
To dynamically allocate an array-based list there should be a parameterized constructor.

54. Overview the order of the operation that determines if an item is in
a list in a sorted, array-based implementation
a list in an unsorted, array-based implementation
a list in a sorted, linked implementation
a list in an unsorted, linked implementation
O(log N)
O(N)
O(N)
O(N)

55. Overview location < length moreToSearch location < length false
// Pre: List contains valid data and List is sorted by key using function // ComparedTo. // There is at most one list item with the same key as item; there may be none. // Post: No list element has the same key as item. List is still sorted. void SortedType::DeleteItem(ItemType item) { int location = 0; int index; bool moreToSearch; moreToSearch = ____________________; bool found = false; while ( !found && _______________) switch (item.ComparedTo(info[location])) { case LESS : location++; break; case GREATER : moreToSearch = _____________________; case EQUAL : ________ = true; } if (found) { for (index = location + 1; index < length; index++) info[index - 1] = ______________; length--;
location < length
moreToSearch
location < length
false
found
info[index]

56. Overview EQUAL index < length length--
// Pre: List contains valid data, sorted by key values. // One and only one list item with the same key as item's is in the list. // Post: No list element has the same key as item; the list is still sorted. void SortedType::DeleteItem(ItemType item) { int location = 0; while (item.ComparedTo(info[location]) != ___________) location++; for (int index = location + 1; ________________; index++) info[index - 1] = info[index]; ___________; }
EQUAL
index < length
length--

57. Overview length - 1 first <= last midPoint - 1 midPoint + 1
ItemType SortedType::GetItem(ItemType& item, bool& found) { // Uses binary search algorithm int midPoint; int first =______________; int last = ______________; bool moreToSearch = _______________; found = false; while (moreToSearch && !found) { midPoint = (first + last) / 2; switch (item.ComparedTo(info[midPoint])) { case LESS : last = _______________; moreToSearch = first <= last; break; case GREATER : first = _______________; moreToSearch = first <= last; case EQUAL : found = true; item =_________________; } return item;
length - 1
first <= last
midPoint - 1
midPoint + 1
info[midPoint]