﻿ C : Insert a new node at the middle of the Linked List

# C Exercises: Insert a new node at the middle of the Linked List

## C Singly Linked List : Exercise-6 with Solution

Write a program in C to insert a node in the middle of a Singly Linked List.

Visual Presentation:

Sample Solution:

C Code:

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

// Structure to define a node in a linked list
struct node
{
int num;                    // Data of the node
struct node *nextptr;       // Address of the next node
}*stnode;                       // Pointer to the starting node

// Function prototypes
void createNodeList(int n);             // Function to create the linked list
void insertNodeAtMiddle(int num, int pos); // Function to insert a node at a given position
void displayList();                     // Function to display the linked list

// Main function
int main()
{
int n, num, pos;

// Displaying the purpose of the program
printf("\n\n Linked List : Insert a new node at the middle of the Linked List :\n");
printf("-----------------------------------------------------------------------\n");

// Inputting the number of nodes for the linked list
printf(" Input the number of nodes (3 or more) : ");
scanf("%d", &n);

// Creating the linked list with n nodes
createNodeList(n);
printf("\n Data entered in the list are : \n");
displayList();

// Inputting data and position to insert in the middle of the list
printf("\n Input data to insert in the middle of the list : ");
scanf("%d", &num);
printf(" Input the position to insert new node : ");
scanf("%d", &pos);

// Checking if insertion is possible at the given position
if(pos <= 1 || pos >= n)
{
printf("\n Insertion cannot be possible in that position.\n");
}
else if(pos > 1 && pos < n)
{
insertNodeAtMiddle(num, pos);
printf("\n Insertion completed successfully.\n");
}

// Displaying the updated list
printf("\n The new list is : \n");
displayList();

return 0;
}

// Function to create a linked list with n nodes
void createNodeList(int n)
{
struct node *fnNode, *tmp;
int num, i;
stnode = (struct node *)malloc(sizeof(struct node));
if(stnode == NULL) // Check whether stnode is NULL for memory allocation
{
printf(" Memory cannot be allocated.");
}
else
{
// Reading data for the first node
printf(" Input data for node 1 : ");
scanf("%d", &num);
stnode->num = num;
stnode->nextptr = NULL; // Links the address field to NULL
tmp = stnode;

// Creates n nodes and adds them to the linked list
for(i = 2; i <= n; i++)
{
fnNode = (struct node *)malloc(sizeof(struct node));
if(fnNode == NULL) // Check whether fnNode is NULL for memory allocation
{
printf(" Memory cannot be allocated.");
break;
}
else
{
printf(" Input data for node %d : ", i);
scanf(" %d", &num);
fnNode->num = num;      // Links the num field of fnNode with num
fnNode->nextptr = NULL; // Links the address field of fnNode with NULL
tmp->nextptr = fnNode; // Links previous node i.e. tmp to the fnNode
tmp = tmp->nextptr;
}
}
}
}

// Function to insert a node at a specified position in the list
void insertNodeAtMiddle(int num, int pos)
{
int i;
struct node *fnNode, *tmp;
fnNode = (struct node*)malloc(sizeof(struct node));
if(fnNode == NULL) // Check whether fnNode is NULL for memory allocation
{
printf(" Memory cannot be allocated.");
}
else
{
fnNode->num = num; // Links the data part
fnNode->nextptr = NULL;
tmp = stnode;
for(i = 2; i <= pos - 1; i++)
{
tmp = tmp->nextptr;
if(tmp == NULL)
break;
}
if(tmp != NULL)
{
fnNode->nextptr = tmp->nextptr;  // Links the address part of new node
tmp->nextptr = fnNode;
}
else
{
printf(" Insertion is not possible at the given position.\n");
}
}
}

// Function to display the linked list
void displayList()
{
struct node *tmp;
if(stnode == NULL)
{
printf(" No data found in the empty list.");
}
else
{
tmp = stnode;
while(tmp != NULL)
{
printf(" Data = %d\n", tmp->num);   // Prints the data of current node
tmp = tmp->nextptr;                 // Advances the position of current node
}
}
}
```
```

Sample Output:

```Linked List : Insert a new node at the middle of the Linked List :
-----------------------------------------------------------------------
Input the number of nodes (3 or more) : 4
Input data for node 1 : 1
Input data for node 2 : 2
Input data for node 3 : 3
Input data for node 4 : 4

Data entered in the list are :
Data = 1
Data = 2
Data = 3
Data = 4

Input data to insert in the middle of the list : 5
Input the position to insert new node : 3

Insertion completed successfully.
The new list are :
Data = 1
Data = 2
Data = 5
Data = 3
Data = 4
```

Flowchart:

createNodeList():

insertNodeAtMiddle() :

displayList() :

C Programming Code Editor:

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