C Program to Insert node at the Beginning of a Singly Linked List | codeitwise

Here we are going to write a c program to insert node at the beginning of a singly linked list. Before we proceed, if you don't have basic knowledge of linked list or want to learn everything about singly linked list at one go then you must visit singly linked list post which is a part of our dsa series and also types of linked list series.

Ok Now How will we do this means insertion of node at the beginning of singly linked list.

We will first allocate memory space for new node. Set its DATA part with the value and the NEXT part is initialized with the address of the first node stored in HEAD. Since we are adding the new node at the beginning i.e., it will be our first node. So now we will point HEAD towards this new node that is HEAD will store the address of this new node.

Algorithm-

Step 1: IF AVAIL = NULL 

    Write OVERFLOW 

    Go to Step 7 [END OF IF] 

Step 2: SET NEW_NODE = AVAIL 

Step 3: SET AVAIL = AVAIL ➡ NEXT 

Step 4: SET DATA = VAL 

Step 5: SET NEW_NODE ➡ NEXT = START 

Step 6: SET START = NEW_NODE 

Step 7: EXIT

C Program to Insert node at the Beginning of a Singly Linked List-

#include <stdio.h>
#include <malloc.h>

struct node
{
    int data;
    struct node* next;
};

void insertatbeg(struct node** head)
{
    int n;
    printf("Enter value to insert at beginning: ");
    scanf("%d",&n);
    struct node* val=(struct node*)malloc(sizeof(struct node));
    val->data=n;
    val->next=*head;
    *head=val;

}
void display(struct node* head)
{
    struct node* t=head;
    while(t!=NULL)
    {
        printf("%d => ",t->data);
        t=t->next;
    }
    printf("NULL \n");
    
}

struct node* head=NULL;
void main()
{
    insertatbeg(&head);
    display(head);
}

Output-

Enter value to insert at beginning: 2
2 => NULL

Visual Representation-