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

Required knowledge:

Algorithm to insert node at the end of Singly linked list

Algorithm to insert node at the end of a Singly Linked List
Begin:
    createSinglyLinkedList (head)
    alloc (newNode)
    If (newNode == NULL) then
        write ('Unable to allocate memory')
    End if
    Else then
        read (data)
        newNode.data ← data
        newNode.next ← NULL
        temp ← head
        While (temp.next != NULL) do
            temp ← temp.next
        End while
        temp.next ← newNode
    End else
End

Steps to insert node at the end of Singly linked list

1. Create a new node and make sure that the address part of the new node points to NULL i.e. newNode->next=NULL
   
   
2. Traverse to the last node of the linked list and connect the last node of the list with the new node, i.e. last node will now point to new node. (lastNode->next = newNode).
   
   

Program to insert node at the end of Singly linked list

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

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


/* Structure of a node */
struct node {
    int data; //Data part
    struct node *next; //Address part
}*head;



void createList(int n);
void insertNodeAtEnd(int data);
void displayList();



int main()
{
    int n, data;

    /*
     * Creates 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();

    /*
     * Inserts data at the end of the singly linked list
     */
    printf("\nEnter data to insert at end of the list: ");
    scanf("%d", &data);
    insertNodeAtEnd(data);

    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
     */
    if(head == NULL)
    {
        printf("Unable to allocate memory.");
    }
    else
    {
        /*
         * Reads data of node from the user
         */
        printf("Enter the data of node 1: ");
        scanf("%d", &data);

        head->data = data; //Links the data field with data
        head->next = NULL; //Links the address field to NULL

        temp = head;

        /*
         * Creates n nodes and adds to linked list
         */
        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; //Links the data field of newNode with data
                newNode->next = NULL; //Links the address field of newNode with NULL

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

        printf("SINGLY LINKED LIST CREATED SUCCESSFULLY\n");
    }
}



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

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

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

        temp = head;

        //Traverse to the last node
        while(temp->next != NULL)
            temp = temp->next;

        temp->next = newNode; //Links the address part

        printf("DATA INSERTED SUCCESSFULLY\n");
    }
}



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

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