C program to insert node at the middle of Singly Linked List

Write a C program to create a singly linked list of n nodes and insert a new node at the middle of the linked list at nth position. How to insert new node at the middle of a singly linked list in C. Algorithm to insert a new node in middle of a singly linked list. Steps to insert new node at any position in singly linked list. Required knowledge

Basic C programming, Functions, Singly linked list, Dynamic memory allocation

Algorithm to insert node at the middle of singly Linked List

Algorithm to insert node at the middle of Singly Linked List
%% Input : n position to insert data in the list
Begin:
alloc (newNode)
If (newNode == NULL) then
write ('Unable to allocate memory.')
End if
Else then
For i ← 2 to n-1
temptemp.next
If (temp == NULL) then
break
End if
End for
If (temp != NULL) then
newNode.nexttemp.next
temp.nextnewNode
End if
End else
End

Steps to insert node at the middle of Singly Linked List

1. Create a new node. 2. Traverse to the n-1th position of the linked list and connect the new node with the n+1th node. Means the new node should also point to the same node that the n-1th node is pointing to. (newNode->next = temp->next where temp is the n-1th node). 3. Now at last connect the n-1th node with the new node i.e. the n-1th node will now point to new node. (temp->next = newNode where temp is the n-1th node). Program to insert node at the middle of Singly Linked List

/**
* C program to insert new node at the middle of Singly Linked List
*/

#include <stdio.h>
#include <stdlib.h>

/* Structure of a node */
struct node {
int data;          // Data

void createList(int n);
void insertNodeAtMiddle(int data, int position);
void displayList();

int main()
{
int n, data, position;

/*
* Create a singly linked list of n nodes
*/
printf("Enter the total number of nodes: ");
scanf("%d", &n);
createList(n);

printf("\nData in the list \n");
displayList();

/*
* Insert data at middle of the singly linked list
*/
printf("nEnter data to insert at middle of the list: ");
scanf("%d", &data);
printf("Enter the position to insert new node: " );
scanf("%d", &position);
insertNodeAtMiddle(data, position);

printf("\nData in the list \n");
displayList();

return 0;
}

/*
* Create a list of n nodes
*/
void createList(int n)
{
struct node *newNode, *temp;
int data, i;

head = (struct node *)malloc(sizeof(struct node));

/*
* If unable to allocate memory for head node
*/
{
printf("Unable to allocate memory.");
}
else
{
/*
* Input data of node from the user
*/
printf("Enter the data of node 1: ");
scanf("%d", &data);

/*
*/
for(i=2; i<=n; i++)
{
newNode = (struct node *)malloc(sizeof(struct node));

/* If memory is not allocated for newNode */
if(newNode == NULL)
{
printf("Unable to allocate memory.");
break;
}
else
{
printf("Enter the data of node %d: ", i);
scanf("%d", &data);

newNode->data = data; // Link the data field of newNode with data
newNode->next = NULL; // Link the address field of newNode with NULL

temp->next = newNode; // Link previous node i.e. temp to the newNode
temp = temp->next;
}
}

}
}

/*
* Creates a new node and inserts at middle of the linked list.
*/
void insertNodeAtMiddle(int data, int position)
{
int i;
struct node *newNode, *temp;

newNode = (struct node*)malloc(sizeof(struct node));

if(newNode == NULL)
{
printf("Unable to allocate memory.");
}
else
{
newNode->data = data; // Link data part
newNode->next = NULL;

/*
* Traverse to the n-1 position
*/
for(i=2; i<=position-1; i++)
{
temp = temp->next;

if(temp == NULL)
break;
}

if(temp != NULL)
{
newNode->next = temp->next;

temp->next = newNode;

printf("DATA INSERTED SUCCESSFULLY\n");
}
else
{
printf("UNABLE TO INSERT DATA AT THE GIVEN POSITION\n");
}
}
}

/*
* Display entire list
*/
void displayList()
{
struct node *temp;

/*
* If the list is empty i.e. head = NULL
*/
{
printf("List is empty.");
}
else
{
while(temp != NULL)
{
printf("Data = %d\n", temp->data); // Print data of current node
temp = temp->next;                 // Move to next node
}
}
}

Output

Enter the total number of nodes: 4
Enter the data of node 1: 10
Enter the data of node 2: 20
Enter the data of node 3: 40
Enter the data of node 4: 50

Data in the list
Data = 10
Data = 20
Data = 40
Data = 50

Enter data to insert at middle of the list: 30
Enter the position to insert new node: 3
DATA INSERTED SUCCESSFULLY

Data in the list
Data = 10
Data = 20
Data = 30
Data = 40
Data = 50

Happy coding 😉 