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CS212:DATA STRUCTURES
Computer Science
Department
Lecture 5: Linked List
linear list Concept
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
Linear list :
 Each

element has a unique successor.
Two approaches to implement a linear list
 Array
 Inefficient
 Linked
when element needs to be inserted or deleted.
list
 Efficient
when element needs to be inserted or deleted.
Categories of linear list
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Linear list Operations
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



Insertion
Deletion
Retrieval
Traversal
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Linked list
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

An ordered collection of data in which each
element contains the location of the next element.
Each element contains two part
 Data
be processed
 Address of the next element
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Linked list-Nodes
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
A node is a structure has at least two fields:
 Data
 Address
of the next node
Data : 6
Address of the next node : 300
Linked list-Nodes
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A node with one data field
number
A node with three data fields
name
id
grdPts
A structure in a node
name
Home_Address
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phone
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Linked List -Head
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
A structure that identifies the list


Head points to the first element in the list
Sometimes used to store metadata(data about the list)

Examples:
Counter : to count the number of element in the list
 Maximum: to store the maximum number in list

Head and Node
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Data Node Structure
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dataType
key <keyType>
field1 <…>
field2 <…>
…
fieldN <…>
end dataType
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Key is included if the
application requires
searching by key
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Common Operations on a Linked List
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Linked List operation
Details
Create a list
Insert a node
Delete a node
Create the head of the list
Search list
Retrieve node
Traverse List
Use a sequential search to find an element in the list
Add data to a linked list
Requires a search algorithm to find the element to be
deleted
Locate data and retrieve it to the calling module
All element are retrieved in sequence
Creating a list
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
Parameter:

Head structure
This algorithm initializes the
metadata of the list.

Creating a list (Pseudocode)
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Insert Node
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Three steps :
1.
Allocate memory for the new node and insert data.
2.
Point the new node to its successor.
3.
Point the new node’s predecessor to the new node
Three cases:
1.
Insert into an empty list
2.
Insert at beginning
3.
Insert at middle
4.
Insert at end.
Insert into an empty list
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The list is empty if the
head points to null.
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Insert at beginning
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The node inserted
before the first node
of the list
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Insert in Middle
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1.Point new node to
its successor
2.Point successor to
the new node
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Insert at end
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1.
2.
Point predecessor
to the new node.
Set new node
(link) to null.
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Inset Node Algorithm
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Inset Node Algorithm (Cont.)
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Delete a node
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Three steps:
1.
Search for the node
2.
Change predecessor link filed to point to the
deleted node successor.
3.
Recycle the node to dynamic memory.
Two cases:
1.
Delete at the beginning
2.
Delete at middle/end
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Delete First Node
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The link of the head points
To node 75.

Figure 3.6
General Delete Case
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
The link of the
predecessor points
to the deleted
node successor
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Delete Node Algorithm
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Delete Node Algorithm (Cont.)
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Search List
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
We need to search the list in order to
 Insert
data
 Delete data
 Retrieve data

Can’t use binary search algorithm with linked list
 No
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physical relationship between the nodes
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Search List
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Doubly Linked Lists
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
The linked list is redefined so that each node in the
list has two pointers, one to the successor and one
to the predecessor.

This list is called a doubly linked list .
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Insert a node at the end of integerdoubly linked list :
Same as single linked list



Connect previous and next links.
Steps:
1. A new node is created, and then its three data
members are initialized
1.
2.
3.
2.
3.
( info member to a number,
next member to null,
and the prev member to value of tail)
tail is set to point to the new node
The next member of the predecessor is set
to point to the new node
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Delete a Node at the end of
Integer-doubly linked list :
A temporary variable (ex. el) is set to the
value in the node.
2. tail is set to its predecessor.
3. The last node is deleted.
4. The next member of the tail node is set to
null.
5. Return the copy of the object stored in the
removed node.
 Note : before deleting, check if the list is
empty.
1.
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Node to be deleted
Circular Lists
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A list where nodes form a ring ; each node
has a successor.
 Example where Circular list is used:

 Several
processes are using the same
resources for the same amount of time, and
each process need a fair share of the
resources.
Circular Lists: Operations
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Same as single linked list



Last node link is connected to the first.
When insert/ delete at the last node
 Make
sure to update the link field of the last node
to the first node.
Insert a node at the front of CLL
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Insert a node at the end of CLL