Lecture Linked List

8/3/2019 Lecture Linked List

1/20

Dr.Aruna Malapati

Asst Professor

Dept of CS & IT

BITS Pilani, Hyderabad Campus

TA C252 COMPUTER PROGRAMMING IIFirst semester 2011-12BITS Pilani Hyderabad campus

Linked List

Todays Agenda


2/20

Abstract Data Type (ADT)

Data type a set of objects + a set of operations

Example: integer

set of whole numbers

operations: +, -, x, /

Can this be generalized? (e.g. procedures generalize the notion of an operator)

Yes!

Abstractdata type high-level abstractions (managing complexity through abstraction)

Encapsulation



3/20

The List ADT

A sequence of zero or more elements

A1, A2, A3, AN

N: length of the list

A1: first element

AN: last element

Ai: position i

If N=0, then empty list

Linearly ordered

Ai precedes Ai+1

Ai follows Ai-1



4/20

Implementation of an ADT

Choose a data structureto represent the ADT

E.g. arrays, records, etc.

Each operation associated with the ADT is

implemented by one or more subroutines

Two standard implementations for the list ADT

Array-based

Linked list



5/20

Array Implementation

Elements are stored in contiguous array positions

Requires an estimate of the maximum size of the list waste space



6/20

Arrays: pluses and minuses

+ Fast element access.

-- Impossible to resize.

Many applications require resizing!

Required size not always immediately available.



7/20

Pointer Implementation

(Linked List)

Ensure that the list is not stored

contiguously

use a linked list a series of structures that are not

necessarily adjacent in memory



8/20

A linked list is a series of connected nodes (or

links) where each node is a data structure.

Dynamically allocated data structures can be

linked togetherto form a chain.

A linked list can grow or shrink in size as theprogram runs. This is possible because the nodes

in a linked list are dynamically allocated.

Linked List ADT



9/20

Linked Lists

Stores a collection of items non-contiguously. Each node stores

element

link to the next node Head: pointer to the first node

The last node points to NULL

A

Head

B C

A

data pointer

node



10/20

Hence a Linked List is a collection of structures ordered not by their

physical placement in memory (like an array) but by logical links

that are stored as part of the data in the structure itself.

Such structure is represented as follows:

struct node

{

int item;struct node *next;

}

node

item next

Self-referentialstructure



11/20

The general node structure

struct tag_name

{

type member1;

type member2;..

struct tag_name*next;

}

next

next

member1 member2 Member N

The structure may contain more thanone item with different types



12/20

Linked-listalso called as one-way list is a collection of data

elements called as nodes.

The linear order is given bypointers.

Each node has two parts.(Data & link field)



13/20


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Example

struct link_list

{

int age;

struct link_list *next;

} ;

main()

{

struct link_list node1,node2;

node1.next=&node2;node1.age=25;

node2.age=56;

}



15/20

struct node

{

int value;

struct node *next;

} *head;



16/20

Advantages oflinked lists

Its a dynamic data structure

Hence it can grow or shrink as needed

It can be made just as long as required

No wastage of memory space

Not necessary to specify the number of nodes

Easy to insert and delete items and rearrangement is very easy



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Limitation oflinked lists

Accessing an arbitrary item is cumbersome and time consuming.

Uses more storage than the array structure. This because of the

additional link field.



18/20

Types of Linked Lists

1. One-way or linear singly linked lists

2. Circular linked lists

3. Two-way or Doubly linked lists

4. Circular doubly linked lists



19/20

Types of Linked Lists

8 12 5 0 Linear list

2 4 8 Circular list

2 4 8 00

Two way linked list

2 4 8

Two way circular listFirst semester 2011-12BITS Pilani Hyderabad campus


20/20

1. What is wrong with the following

declaration?

struct element

{ double value;

struct element link;} ;


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Lecture Linked List

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