This document discusses singly linked lists and their insertion operations. It describes: - A singly linked list consists of nodes where each node has a data field and pointer to the next node. - There are three ways to insert a node: at the front by changing the head pointer, at the end by traversing to the last node, and at any position p by finding the predecessor node. - Pseudocode is provided for functions to insert at the front, end, and at a given position p by updating the next pointers of the predecessor and new nodes.

1. Singly Linked List
A Linear Data Structure
SONI GUPTA
ASSISTANT PROFESSOR (NPIU-TEQIP III )
HBTU KANPUR, UP
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2. Insertion Operation

3.  A linked list consists of nodes where each node contains a data field and a
reference(link/pointer) to the next node in the list.
 A node in the singly linked list consist of two parts: data part and link part.
 Data part of the node stores actual information
 Next part of the node stores the address of its immediate successor.
 Singly linked list can be traversed only in one direction
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head

5. Node creation
struct node
{
int data;
struct node *next;
};
struct node *head, *ptr;
ptr = (struct node *)malloc(sizeof(struct node *));
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6. Insert at first position
 Inserting any new node at the front of the list.
 Insert_at_First
1. Create a new empty Node
2. Initialize the data field and Next field
3. Set the address pointer of head and newnode
4. Return address of new node (Set the head of node to new node)
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7.  head
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8. head
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x
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9. head
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x
newNode
newNode→next=head
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10. 10 20
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head
Head=newNode
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11. Create a New Node
𝑛𝑜𝑑𝑒 𝑐𝑟𝑒𝑎𝑡𝑒𝑁𝑜𝑑𝑒(){
struct *𝑛𝑜𝑑𝑒 𝑛𝑒𝑤𝑁𝑜𝑑𝑒;
𝑛𝑒𝑤𝑁𝑜𝑑𝑒 = (𝑛𝑜𝑑𝑒)𝑚𝑎𝑙𝑙𝑜𝑐(𝑠𝑖𝑧𝑒𝑜𝑓(𝑠𝑡𝑟𝑢𝑐𝑡 𝐿𝑖𝑛𝑘𝑒𝑑𝐿𝑖𝑠𝑡));
𝑛𝑒𝑤𝑁𝑜𝑑𝑒→𝑛𝑒𝑥𝑡 = 𝑁𝑈𝐿𝐿;
𝑟𝑒𝑡𝑢𝑟𝑛 𝑛𝑒𝑤𝑁𝑜𝑑𝑒;
}
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12. node insert_at_Front(node head, int value){
node newNode;
newNode = createNode();
newNode →data = value;
if(head == NULL){
head = newNode; //when linked list is empty
}
else{
newNode→next = head;
head= newNode;
}
return head;
}
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13. Insert at last position
1. Create a new node
2. Initialize the data and next field
3. Check if the list is empty (New node will be the first and last node)
4. Initialize search for the last node
5. Set next field of last node to new node
6. Return head pointer
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14.  head
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newNode
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15.  head
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newNode
p
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16.  head
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newNode
p
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17. //Insert node at the end of the linked list
node insert_at_End(node head, int value){
node newNode,p;
newNode = createNode();
newNode→data = value;
if(head == NULL){
head = newNode; //when linked list is empty
}
else{
p = head;
while(p->next != NULL){
p = p->next;
}
p->next = newNode;
}
return head;
}
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18. Insert at any position p
1. Create a new node
2. Initialize the data and next field
3. Check if the list is empty (New node will be the first and last node)
4. Initialize temporary pointer
5. Initialize search for the predecessor of new node
6. Set next field of predecessor and new node
7. Return head pointer
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19.  head
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newNode
p
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20.  head
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newNode
pp
1. newNode→next=p →next
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21.  head
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newNode
pp
2. p → next=newNode
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22. void insert_at_pos(node head, int value)
{
int i,pos;
struct node *newNode, *temp;
newNode = (struct node *) malloc (sizeof(struct node));
if(head == NULL)
{
printf("n list is empty");
}
else
{
newNode→data = value;
printf("nEnter the location after which you want to insert the new node ");
scanf("n%d",&pos);
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23. temp=head;
for(i=0;i<pos;i++)
{
temp = temp →next;
if(temp == NULL)
{
printf("ncan't insertn");
return;
}
}
newNode →next = temp →next;
temp →next = newNode;
printf("nNode inserted at given location");
}
}
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24. Complexity
 Traverse/Access- O(n)
 Search- O(n)
 Insertion- O(1)
 Deletion- O(1)
** Insertion and deletion will take O(n) time if you need to first traverse the list and
then insert or delete.
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