11 Linked Lists_JAVA 01

8/10/2019 11 Linked Lists_JAVA 01

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Linked Lists

Reading: Savitch, Chapter 10


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Objectives

To learn

what is a linked list

how to declare a linked list in JAVA

how to create and traverse a linked list


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Motivation

Write a program to store information about

a class of students (eg., names, results, etc)

Problems associated with use of an array

how big should the array be?

too small => ?

too big => ?

Other examples: address book, dictionary


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Dynamic structures

Grow and diminish dynamically based on

the program requirement.


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Linked List

What is a linked list?

a variable-length collection of objects (of

the same class). Each object is called a

node of the linked list. Each node

contains a reference to the next node.


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A linked list

head

data data data


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Linked list declaration

class StudentNode {

private String name;

private int mark;

private StudentNode next;

public StudentNode(String _n, int _m)

{ name = _n; mark = _m;

next = null;}

... ...

}

class LinkedList {private StudentNode head = null;

... ...

}

Ahmed

67

Kim

84

head

version 1


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Linked list declaration

Alternatively, theStudentNode

class can bedefined as an inner class ofLinkedList.

class LinkedList {

private StudentNode head = null;

... ...private class StudentNode {

private String name;

private int mark;

private StudentNode next;

public StudentNode(String _n, int _m) {

name = _n; mark = _m;

next = null;

}

... ... version 2}

}


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A linked list

Ahmed

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Sally

48

Kim

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null

head


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Adding to a linked list

Ahmed

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Sally

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Kim

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null

head

Add Pablo to list


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Adding to a linked list

Ahmed

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Sally

48

Kim

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head

Pablo

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null

Add Pablo to list


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Deleting from a linked list

Ahmed

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Sally

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Kim

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head

Pablo

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null

Delete Sally from list


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Deleting from a linked list

Ahmed

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Kim

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head

Pablo

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null

Delete Sally from list


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Accessing elements

Ahmed

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head

Accessing the first element

head.mark

head.name

is this using version 1 or 2 ?


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Insertion at front of list

Ahmed

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Kim

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Pablo

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head

NULL

Add a node for student called Janice whohas a mark of 89


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Insertion (ctd)

Design

create a new node

fill in its data fields

connect the node to the front of the list

change headso that it points to the newnode


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Insertion (ctd)

Ahmed

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Kim

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Pablo

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head

null

Add a node for a student called Janice whohas a mark of 89

Janice

89


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Insertion (ctd)

Ahmed

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Kim

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Pablo

56

head

null


Janice

89


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Insertion (ctd)

Ahmed

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Kim

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Pablo

56

head

null


Janice

89


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Insertion (ctd)

Ahmed

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Kim

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Pablo

56

head

null

Janice

89



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Insertion (ctd)

StudentNode p = new StudentNode

(Janice, 89);

p.next = head;

head = p;

JAVA source code


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Insertion (ctd)


(Janice, 89);

p.next = head;

head = p;

Ahmed

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Kim

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Pablo

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head

null


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Insertion (ctd)


(Janice, 89);

p.next = head;

head = p;

Ahmed

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Kim

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Pablo

56

head

null

p

Janice

89

null


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Insertion (ctd)


(Janice, 89);

p.next = head;

head = p;

Ahmed

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Kim

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Pablo

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head

NULL

p

Janice

89


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Insertion (ctd)


(Janice, 89);

p.next = head;

head = p;

Ahmed

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Kim

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Pablo

56

head

NULL

p

Janice

89


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Building a linked list

To create a linked list:

head = nullwhile more nodes

insert a node at front of list


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Printing a linked list

Ahmed

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Kim

84

Pablo

56

head

null


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Printing a linked list (ctd)

start at the head of the list

while there is a node

print data of the node

move to the next node on the list

Pseudocode


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Printing a linked list (ctd)

StudentNode p = head;

while (p != null) {

System.out.println (p.name + : + p.mark);

p = p.next;

}

JAVA source code


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while (p != null)

{

System.out.println (p.name + : +

p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

Printing a linked

list (ctd)


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while (p != null)

{


p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Printing a linked

list (ctd)


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while (p != null)

{


p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Printing a linked

list (ctd)

Printing a linked


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while (p != null)

{


p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Ahmed: 67

Printing a linkedlist (ctd)

Printing a linked


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while (p != null)

{

System.out.println (p.name + :

+ p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Ahmed: 67


Printing a linked


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while (p != null)

{


+ p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Ahmed: 67


Printing a linked


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while (p != null)

{


+ p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Ahmed: 67Kim: 84


Printing a linked


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while (p != null)

{


+ p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Ahmed: 67Kim: 84


Printing a linked


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while (p != null)

{


+ p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

Ahmed: 67Kim: 84



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St d tN d h d

Printing a linked


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while (p != null)

{


+ p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

null

Ahmed: 67Kim: 84Pablo: 56


St d tN d h d

Printing a linked


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while (p != null)

{


+ p.mark);

p = p.next;

}

Ahmed

67

Kim

84

Pablo

56

head

null

p

null

Ahmed: 67Kim: 84Pablo: 56



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Linked list example

Problem

write pseudocode to work out the average mark

of the students in the linked listconvert the pseudocode to JAVA code


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Calculate the average markStudentNode p = head;

int avMark = 0, numberSt = 0;

while (p != null) {

System.out.println (p.name + : + p.mark);

avMark = avMark + ____________;_____________;

p = p.next;

}

if (numberSt == 0)______________;

else

______________;

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11 Linked Lists_JAVA 01

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