Insert at Beginning of Circular Linked List in DSA Python - Build from Scratch

Insert at Beginning of Circular Linked List

📖 Scenario: You are managing a circular linked list that represents a round-robin queue of tasks. You need to add a new task at the beginning of the queue so it gets priority.

🎯 Goal: Build a circular linked list and write code to insert a new node at the beginning, maintaining the circular structure.

📋 What You'll Learn

Create a Node class with data and next attributes

Create a circular linked list with three nodes containing data 10, 20, and 30

Create a function insert_at_beginning(head, data) that inserts a new node at the start

Print the circular linked list starting from the head after insertion

💡 Why This Matters

🌍 Real World

Circular linked lists are used in real-world systems like task schedulers, multiplayer games turn management, and buffering data streams where the list loops back to the start.

💼 Career

Understanding circular linked lists and insertion operations is important for software engineers working on system programming, embedded systems, and applications requiring efficient cyclic data management.

1

Create the Circular Linked List with 3 Nodes

Create a class called Node with attributes data and next. Then create three nodes with data 10, 20, and 30. Link them in a circular way so that the last node points back to the first node. Assign the first node to a variable called head.

DSA Python

# Define Node class and create circular linked list with nodes 10, 20, 30
# Your code here

Hint

Remember to make the last node point back to the first node to form a circle.

2

Create a Function to Insert at Beginning

Create a function called insert_at_beginning(head, data) that creates a new node with the given data and inserts it at the beginning of the circular linked list. The function should return the new head of the list.

DSA Python

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3
node3.next = node1

head = node1

# Define insert_at_beginning function below
# Your code here

Hint

Traverse to the last node to update its next pointer to the new node.

3

Insert a New Node with Data 5 at Beginning

Use the function insert_at_beginning(head, 5) to insert a new node with data 5 at the beginning of the circular linked list. Update the head variable to the returned new head.

DSA Python

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3
node3.next = node1

head = node1

def insert_at_beginning(head, data):
    new_node = Node(data)
    if head is None:
        new_node.next = new_node
        return new_node
    else:
        temp = head
        while temp.next != head:
            temp = temp.next
        temp.next = new_node
        new_node.next = head
        return new_node

# Insert new node with data 5 at beginning and update head
# Your code here

Hint

Call the function and assign its result back to head.

4

Print the Circular Linked List Starting from Head

Write code to print the circular linked list starting from head. Print each node's data followed by ->. Stop printing when you reach the head again. End the output with null.

DSA Python

Hint

Use a while True loop and break when you reach the head again.