Singly & Circular Linked list

Singly &
Circular
Linked List
Presented by
Md. Zabirul Islam
Md. Sharzul Mostafa
Manon Rahman
Aparajita Dola and
Shahriar Parvej
Department of CSE, KUET

Outlines
 Introduction
 Advantage of a Link List over Array
 Link List Declaration
 Basic Link List Operation
 Circular Link List
 Application
 Disadvantage
Computer Science & Engineering , KUET 01/43

Introduction
What Is Linked List?
 The most commonly used data structure to store data in memory.
 A linear collection of data elements, called nodes.
 Unlike arrays, linked list elements are not stored at adjacent location.
 The nodes connect by pointers.

What’s wrong with Array and Why linked lists?
 Insertions and deletions are simple and faster.
 Linked list is able to grow in size.
 Linked List reduces the access time.
 No wastage of memory.
 Disadvantages of arrays as storage data structures:
Linked lists solve some of these problems :
Insertion and deletion operations are slow.
Slow searching in unordered array.
Wastage of memory.
Fixed size.

Singly Linked List
Singly linked list is a collection of nodes.
Each node contains two parts.
 The data contains elements .
 Link contains address of next node .
data link
Node

Structure of singly linked list
linkdata
A B C
linklink datadata
head
 The head always points to the first node .
 All nodes are connected to each other through Link fields.
 Null pointer indicated end of the list.
X

Circular linked list
A circular linked list is one which has
 No ending.
 The null pointer in the last node of a linked list is replaced with the
address of its first node .

Structure of circular linked list
CIRCULAR LINKED LIST:-
4000 1000 2000
B 2000 C 4000A 1000

Operations on linked list
The basic operations on linked lists are :
1. Creation
2. Insertion
3. Deletion
4. Traversing
5. Searching

The creation operation is used to create a linked list.
Declare Node struct for nodes.
 Data - any type
 Link - a pointer to the next node.
Struct node{
int data;
Struct node *link;
}
What Is creation

 Allocate a new node
 Insert new element
 Make new node point to null
 Create head to point to new node
Algorithm
 create a new node
 new->data=item
 new->link=NULL
 head=new
What Is creation

Creation
 new->data=item
 new->link=NULL
 head=new
X
head
New Node
A

What Is Insertion
Insertion operation is used to insert a new node in the
linked list at the specified position.
When the list itself is empty , the new node is inserted
as a first node.

Types of Insertion
There are many ways to insert a new node
into a list :
 As the new first element.
 As the new last element.
 Before a given value.
 After a given value.

Inserting at the beginng
 Make new nodetopoint to old head
 Update head topoint to new node
Algorithm
 new->data=item
 new->link=head
 head=new

Inserting at the beginning
X
linklink datadata
head
New Node
B C
A
 new->link=head
 head=new

Inserting at the last
 Searching the last node
 Have old last node point to new node
 Update new node that point to null
 new->data=item
 ptr=head while(ptr->link!=null) ptr=ptr>link
 ptr->link=new
 new->link=NULL
Algorithm

Inserting at the last
B C
linklink datadata
A
X
New Node
head
ptr->link=new
new->link=NULL

Inserting before given a value
 Searching the given node
 Store the previous node
 Update new to point to previous node link
 Update previous node to point to new
node
 new->data=item
 ptr=head while(ptr->info!=data) temp=ptr
ptr=ptr>link
 new->link=temp->link
 temp->link=new
 Algorithm

Inserting before given a value
linkdata
A
X
B
linklink datadata
head
New Node
D
C
temp ptr
new->link=temp->link
temp->link=new

Inserting after given a value
 Allocate a new node, new
 Searching the node
 Update new to point to the link of the
given node
 Update given node to point to new
node
 new->data=item
 ptr=headwhile(ptr->info!=data) ptr=ptr>link
 new->link=ptr->link
 ptr->link=new
 Algorithm
 Algorithm

Inserting after given a value
linkdata
A
X
B
linklink datadata
New Node
D
C
ptr
head
new->link=ptr->link
ptr->link=new

What Is Deletion?
Deletion operation is used to delete a particular node in
the linked list.
we simply have to perform operation on the link of the
nodes(which contains the address of the next node) to
delete a particular element.

Types of Deletion
Deletion operation may be performed in
the following conditions:
 Delete first element.
 Delete last element.
 Delete before a given value.
 Delete after a given value.
 Delete a particular element

Deleting the first node
 Declare anode
 Assignheadtothenewnode
 Update head with thelinkof the
new node
Algorithm
 srt=head
 head=srt->link

X
linklink datadata
head
data link
B CA
 srt=head
 head=srt->link
srt

Deleting the last node
 Declare nodessrt,temp
 Traversethelistandupdate temp
withthevalueofsrt
 IfthelinkofsrtisNULL,updatethelink
oftempwithNULLandbreaktheloop
Algorithm
declare srt, temp
for(srt=head;;temp=srt,
srt=srt->link)
if(srt->link==NULL)temp-
>link=NULL;Exit;

Deleting the last node
X
linklink datadata
head
data link
B CA
X

Deleting after a given value
 Declare a node srt
 Search the element to delete after
 Update link of the node with the link of the
next node
 Node *srt
 srt=head while(srt->info!=data) srt=srt>link
 srt->link=srt->link->link
 ptr->link=new
 Algorithm
 Algorithm

linkdata
A
X
B
linklink datadata
C
srt
head
C

Deleting before a given value
 Declare nodes srt, temp and prev
 Search the element to delete before
 Update link of the previous node with the
link of the next node
 Node *srt, *temp, *prev
 srt=head while(srt->info!=data) srt=srt>link
 prev = temp; temp = srt;
 Prev->link = srt
 Algorithm
 Algorithm

Deleting before a given value
linkdata
A B
linklink datadata
C
prev
head
X
D
linkdata
temp srt

Deleting a given value
 Declare nodes srt and temp
 Search the element to delete
 Update link of the previous node with
the link of the selected node
 Node *srt, *temp
 Srt=head while(srt->info!=data) srt=srt->link
 temp = srt;
 temp->link = srt->link
 Algorithm
 Algorithm

linkdata
A B
linklink datadata
C
head
X
D
linkdata
temp srt

Operations on a singly circular linked list
 The basic operations on singly circular linked lists are :
1. Creation
2. Insertion
3. Deletion
4. Traversing
5. Searching

 Creation of a circular linked list is same as singly list except that we will have to
use head instead of NULL
 To traverse the list we have to start from head and end until the link of a node is
head
 To insert a node at the beginning of the list we have to store the value of head
in a temporary node and operate accordingly
The operations on a singly circular linked is almost same as that of a singly
linked list. The only difference between them is that the link of the last node of
a singly linked list contains NULL, whereas that of a circular list contains head

 The operation insert last, is almost the same as that of the singly list, difference: head
instead of NULL in the link of new node
 The operation insert after, is same as that of the singly list. If the node is the last node
then we can perform the operation just by calling the insert last’s function
 The operation insert before, is same as that of the singly list
 The operation delete after and before, is same as that of the singly list. Deleting last
element is also almost the same, only have to update the link of previous node with
head. But the process of deleting the first element is different, it’ll be discussed in this
presentation
 The operation delete element, is same as that of the singly list

 Mostoftheoperationsarealmostthesameassinglylinkedlistincaseofasingly
circularlinkedlist, onlyalittlevariationinlistcreationanddeletingthefirstelement,
nextcontentscontaintheseoperations!

 Make new node point to head
 Update head to point to new nodeoffirst
element
 Ifnotfirstelementupdatelinkofprevious
elementwithcurrentnodeaddress
Algorithm
 new->data=item
 new->link=head
 head=new, temp=new, if
head==NULL
 else temp->link=new,
temp=ptr
Creation of a circular list

Creation
head
New Node
A
headhead
B
New Node
 new->data=item
 new->link=head

 Declare anewnode,srt
 Assignheadtothenewnode
 Update head with thelinkof thenew
node
 Update thelinkoflastnode with thelink
of thenew node
Algorithm
 srt=head
 head=srt->link
 last->link=head

head
linklink datadata
head
data link
B CA
last
 head=srt->link
 last->link=head

Application
Linked lists are used in many other data structures.
Linked lists are used in polynomial manipulation.
Representation of trees, stacks, queues. etc.

Disadvantages of Linked Lists
 The memory is wasted as pointers require extra memory for storage.
 No element can be accessed randomly.
 It has to access each node sequentially.
 Reverse Traversing is difficult in linked list.
 No binary search.

Singly & Circular Linked list

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