Insert at Beginning Head Insert in DSA C - Build from Scratch

Insert at Beginning (Head Insert) in a Linked List

📖 Scenario: Imagine you are managing a guest list for a party. New guests arrive and you want to add each new guest to the front of the list so they are greeted first.

🎯 Goal: You will build a simple linked list in C and learn how to insert new nodes at the beginning (head) of the list.

📋 What You'll Learn

Create a linked list node structure with an integer data field and a next pointer

Create a pointer head to represent the start of the list

Write a function insertAtBeginning to add a new node at the start

Insert three nodes with values 10, 20, and 30 at the beginning in that order

Print the linked list after all insertions showing the order of nodes

💡 Why This Matters

🌍 Real World

Linked lists are used in many applications like managing playlists, undo functionality in apps, and dynamic memory management.

💼 Career

Understanding linked lists and how to insert nodes is fundamental for software developers working with data structures and memory management.

1

Create the linked list node structure and initialize head

Write the struct definition for a linked list node named Node with an int data and a Node* pointer named next. Then create a Node* variable called head and initialize it to NULL.

DSA C

# Define the Node struct and initialize head
// Your code here

Hint

Use typedef struct Node { int data; struct Node* next; } Node; and set head to NULL.

2

Create the insertAtBeginning function

Write a function called insertAtBeginning that takes an int value parameter. Inside, create a new Node* using malloc, set its data to value, set its next to the current head, then update head to this new node.

DSA C

# Write insertAtBeginning function
// Your code here

Hint

Allocate memory for a new node, set its data, point its next to head, then update head.

3

Insert nodes with values 10, 20, and 30 at the beginning

Call the insertAtBeginning function three times to insert the values 10, 20, and 30 in that order.

DSA C

// Insert 10, 20, and 30 at the beginning
// Your code here

Hint

Call insertAtBeginning three times with 10, 20, and 30.

4

Print the linked list to show the order of nodes

Write a printList function that starts from head and prints each node's data followed by ->. After printing all nodes, print NULL. Then call printList() in main after the insertions.

DSA C

# Write printList function and call it in main
// Your code here

Hint

Traverse from head, print each node's data followed by '->', then print 'NULL'.