Chapter 3

ADTs unsorted List and Sorted List

3-2

List Definitions

Linear relationship Each element except the first has a unique predecessor, and each element except the last has a unique successor.

Length The number of items in a list; the length can vary over time.

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List Definitions

Unsorted list A list in which data items are placed in no particular order; the only relationship between data elements is the list predecessor and successor relationships.

Sorted list A list that is sorted by the value in the key; there is a semantic relationship among the keys of the items in the list.

Key The attributes that are used to determine the logical order of the list.

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Assumptions for All our Lists

1. Our lists are composed of unique elements.

2. When sorted, our lists are sorted from the smallest to largest key value.

3. We use the “by copy” approach.

4. We use the programming “by contract” approach.

Development of an Unsorted List ADT:

UnsortedStringList

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Unsorted List ADT Specification

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Constructors

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Observers

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Transformers

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Iterators

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Application Level

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List Design Terminology

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Instance Variables of Unsorted List ADT

3-14

Beginning of Unsorted StringList Class:

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Constructors

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Definitions

• Signature The distinguishing features of a method heading. The combination of a method name with the number and type(s) of its parameters in their given order.

• Overloading The repeated use of a method name with a different signature.

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Simple Observers

public boolean isFull ( )

// Returns whether this lis is full

{

return (list.length == numItems);

}

3-18

isThere Operation

3-19

Retrieving an Item in an Unsorted List

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Retrieving an Item in an Unsorted List

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insert Operation

3-23

Deleting Bobby (move up)

• public void delete (String item)• // Deletes the element that matches item from this list• {• int location = 0;• while (item.compareTo(list[location]) != 0)• location++;• If(isThere(item)• {• For( int I = location; i,<numItm-1;i++)• list[i] = list[i+1];• }• }

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Deleting Bobby (swap)—more efficient

• public void delete (String item)• // Deletes the element that matches item from this list• {• int location = 0;• while (item.compareTo(list[location]) != 0)• location++;• list[location] = list[numItems - 1];• numItems--;• }

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UML Diagram of UnsortedStringList

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Reuse Operations

Ways we could reuse the code of the Unsorted List ADT to create the code for the Sorted List ADT:

1. Cut and Paste—”cut and paste” the code that we are able to reuse into the new file.

2. Direct Inheritance—have the Sorted List ADT inherit methods from the Unsorted List ADT.

3. Abstract Classes—resolve the deficiencies of both of the previous approaches.

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Steps for Using Abstract Class Approach

1. We first create an abstract list class.1. Its concrete methods provide the operations that

our two list ADTs share in common.

2. Its abstract methods provide the operations that are not shared.

2. Then create two concrete classes that extend the abstract list class.1. One that implements an unsorted list

2. The other that implements a sorted list

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The Abstract Class

• Please click on the following link Programs/C03P165.jpg to view the appropriate program.

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Extending the Abstract Class

• Please click on the following link Programs/C03P166.jpg to view the appropriate program.

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UML Diagram

Abstract Data Type Sorted List

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Sorted List ADT Specification (partial)

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Constructors

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Redefined insert

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Redefined Delete

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insert Operation

1. Find the place where the new element begins.

2. Create space for the new element.

3. Put the new element on the list.

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Original List

3-39

Insert Becca

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Result

3-41

insert (item)

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3-43

delete (item)

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3-45

Binary Search Algorithm

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isThere (item): returns boolean

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UML Diagram

• Please click on the following link Programs/C03P180.jpg to view the appropriate program.

3-53

Comparison of Algorithms

Big-O Notation A notation that expresses computing time (complexity) as the term in a function that increases most rapidly relative to the size of a problem

Iff(N) = N4 + 100N2 + 10N + 50

then f(N) is 0(N4). N represents the size of the problem.

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Comparison of Rates of Growth

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Comparison of Linear and Binary Searches

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Big-O Comparison of List Operations

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Generic ADTsSo far…• An unsorted list of strings• An unsorted list of strings that extended

String List• A sorted list of strings that extended

String ListNext—• Lists of generic dataGeneric Data Type A type for which the

operations are defined but the types of the items being manipulated are not

3-58

The Listable Interface

3-59

A ListCircle Class

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A Generic Abstract List Class

• Please click on the following link Programs/C03P196.jpg to view the appropriate program.

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3-62

A Generic Sorted List ADT

• Please click on the following link Programs/C03P200.jpg to view the appropriate program.

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UML Diagrams for our List Framework

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A Listable Class

• Please click on the following link Programs/C03P204.jpg to view the appropriate program.

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Using the Generic List

To Create a sorted list of strings use either of its constructors:

SortedList list1 = new SortedList();SortedList list2 = new SortedList (size);

Declare at least one object of class ListStringListString aString;

Instantiate ListString objects and place them on the list.

aString = new ListString(“Amy”);list.insert(astring)