Linked list data structure

1. LINKEDLIST
MODULE 3
Dr. SINDHIA LINGASWAMY, VIT 1

2. TOPICS COVERED
• Definition
• Representation of linked list
• Operations of linked list
• Implementation of the list
• Array implementation
• Linked list implementation
• Cursor implementation
• Ajflajf
Dr. SINDHIA LINGASWAMY, VIT 2

3. DEFINITION
• Linear collection of data elements called nodes.
• Linked list is a sequence of links which contains items. Each link contains
a connection to another link.
• Important terms to understand the concept of linked list.
• Link − each link of a linked list can store a data called an element.
• Next − each link of a linked list contains a link to the next link called next.
• Linked list − a linked list contains the connection link to the first link
called first.
Dr. SINDHIA LINGASWAMY, VIT 3

4. REPRESENTATION OF LINKED LIST
Dr. SINDHIA LINGASWAMY, VIT 4
H D1
NEXT
D2
NEXT
D3
NEXT
• Linked List contains a link element called first / Header.
• Each node carries a data field(s) and a link field called next.
• Each node is linked with its next node using its next link.
• Last node carries a link as null to mark the end of the list.

5. OPERATIONS
• The basic operations supported by a list.
• Insert(X,Y) − insert an element X at the position Y.
• Deletion(X) − deletes an element X.
• Find(X) − Returns the position of X
• Next (i) – Returns the position of its successor element i+1
• Previous (i)- Returns the position of its predecessor i-1
• Display − Print the complete list.
• MakeEmpty − Makes the list empty.
Dr. SINDHIA LINGASWAMY, VIT 5

6. TYPES OF LINKED LIST
•Singly linked list
•Doubly linked list
•Circular linked list
Dr. SINDHIA LINGASWAMY, VIT 6

7. SINGLY LINKED LIST
• A linked list which each node contains only one link positioning to
the next node in the list.
Dr. SINDHIA LINGASWAMY, VIT 7
H 10 20 30
20 30 4010

8. DECLARATION OF LINKED LIST
Struct node;
typedef struct Node *List;
typedef struct Node *Position;
int IsLast( Position P, List L);
int IsEmpty(List L);
position Find (int X, List L);
void Delete (int X, List L);
position FindPrev(int X, List L);
position FindNext(int X, List L);
void Insert(int X, List L, Position P);
void DeleteList(List L);
Struct Node
{
int element;
position Next;
}
Dr. SINDHIA LINGASWAMY, VIT 8

9. INSERTION
void Insert ( int X, List L, Position P)
{
position Newnode;
Newnode = malloc(size of (Struct Node));
if (Newnode != NULL )
{
Newnode → Element = X;
Newnode → Next = P → Next ;
P → Next = Newnode;
}
}
Dr. SINDHIA LINGASWAMY, VIT 9

10. Dr. SINDHIA LINGASWAMY, VIT 10
H 10 20 30
15
P
Newnode

11. ISEMPTY
• Check whether the list is empty
int IsEmpty ( List L )
{
if ( L → Next == NULL )
return (1);
}
Empty List
Dr. SINDHIA LINGASWAMY, VIT 11
Header L

12. ISLAST
• Check whether the current position is last.
int IsLast ( position P, List L )
{
if ( P → Next == NULL);
return (1);
P
}
Dr. SINDHIA LINGASWAMY, VIT 12
L 10 20 30

13. FIND
•Returns the position of X
position Find (int X, List L)
{
position P;
P = L → Next ;
while ( P ! = NULL && P → Element ! = X)
P = P → Next;
return P; P
}
Dr. SINDHIA LINGASWAMY, VIT 13
L 10 20 30

14. PREVIOUS
position FindPrev (int X, List L)
{
position P;
P = L;
while ( P → Next ! = NULL && P → Next → Element != X)
P = P → Next ;
return P;
}
P X
Dr. SINDHIA LINGASWAMY, VIT 14
L 10 20 30

15. FINDNEXT
position FindNext ( int X, List L)
{
P = L → Next;
while ( P → Next ! = NULL && P → Element ! = X)
P = P → Next ;
return P → Next;
}
X, P P → Next
Dr. SINDHIA LINGASWAMY, VIT 15
L 10 20 30

16. Delete an Element
void Delete (int X, List L)
{ X
position P, Temp;
P = FindPrev( X,L );
if ( ! IsLast ( P, L)) P Temp
{
Temp = P → Next;
P → Next = Temp → Next;
Free (Temp);
}
}
Dr. SINDHIA LINGASWAMY, VIT 16
L 10 20 30
L 10 30

17. DELETE THE LIST
Void DeleteList ( List L)
{
position P, Temp;
P = L → Next;
L → Next = NULL;
while ( P ! = NULL )
{
Temp = P → Next;
free (P);
P = Temp;
}
}
Dr. SINDHIA LINGASWAMY, VIT 17

18. Dr. SINDHIA LINGASWAMY, VIT 18
L 10 30
10 30
30
L → Next = NULL
Temp = P → Next
P
P Temp
Free ( P )
P = Temp
Temp , P = NULL

19. DOUBLY LINKED LIST
◦ Doubly linked list is a linked data structure that consists of a set of
sequentially linked records called nodes.
◦ Each node contains three fields
◦ one is data part which contain data only.
◦ two other field is links part that are point or references to the
previous or to the next node in the sequence of nodes.
◦ The beginning and ending nodes' previous and next links,
respectively, point to some kind of terminator, typically a sentinel
node or null to facilitate traversal of the list.
Dr. SINDHIA LINGASWAMY, VIT 19

20. REPRESENTATION
Dr. SINDHIA LINGASWAMY, VIT 20
20 300 1000 30 5700 300 40

21. COMPARED WITH SLL
◦ Advantages
◦ Can be traversed in either direction (may be essential for some
programs)
◦ Some operations, such as deletion and inserting before a node,
become easier
◦ Disadvantages
◦ Requires more space
◦ List manipulations are slower (because more links must be changed)
◦ Greater chance of having bugs (because more links must be
manipulated) Dr. SINDHIA LINGASWAMY, VIT 21

22. INSERTION
Dr. SINDHIA LINGASWAMY, VIT 22
20 30 40
H
25
L
P
NEW NODE

23. ROUTINE – INSERTION
void Insert ( int X, list L, position P )
{
Struct Node *Newnode;
Newnode = malloc )sizeof (Struct Node));
If ( Newnode ! = NULL )
{
Newnode → Element = X;
Newnode → Flink = P → Flink;
P→Flink→Blink = Newnode;
P→Flink = Newnode;
Newnode →Blink = P;
} } Dr. SINDHIA LINGASWAMY, VIT 23

24. DELETION
Dr. SINDHIA LINGASWAMY, VIT 24
20 30 40
H
P

25. ROUTINE – DELETION
void Delete ( int X, List L)
{
position P;
P = Find(X,L);
if ( IsLast(P,L))
{
Temp = P ;
P→Blink→Flink – NULL;
free (Temp);
}
else
{
Temp = P;
P→Blink →Flink = P →Flink;
P→Flink→Blink = P→Blink;
Free (Temp);
}
}
Dr. SINDHIA LINGASWAMY, VIT 25

26. CIRCULAR LINKED LIST
• The pointer of the las t node points to the first node
• Can be implemented as
• Singly linked circular list
• Doubly linked circular list
Dr. SINDHIA LINGASWAMY, VIT 26
5700 20 300 1000 30 5700 300 40 1000
10 20 30