Python program to insert a new node at the end of the Circular Linked List

When it is required to insert a new node at the end of the circular linked list, a Node class needs to be created. In this class, there are two attributes: the data that is present in the node, and the access to the next node of the linked list.

In a circular linked list, the head and the tail are adjacent to each other. They are connected to form a circle, and don't have NULL value in the last node. Instead, the last node points back to the first node.

Another class needs to be created that would have an initialization function, and the head of the node would be initialized to None.

Implementation

Below is a demonstration of inserting nodes at the end of a circular linked list ?

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

class CircularLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None
    
    def add_at_end(self, data):
        new_node = Node(data)
        
        # If list is empty
        if self.head is None:
            self.head = new_node
            self.tail = new_node
            new_node.next = self.head  # Point to itself
        else:
            # Add after tail and update connections
            self.tail.next = new_node
            self.tail = new_node
            self.tail.next = self.head  # Maintain circular structure
    
    def print_list(self):
        if self.head is None:
            print("The list is empty")
            return
        
        current = self.head
        result = []
        
        # Print first node
        result.append(str(current.data))
        current = current.next
        
        # Print remaining nodes until we reach head again
        while current != self.head:
            result.append(str(current.data))
            current = current.next
        
        print(" -> ".join(result) + " -> (back to head)")

# Create circular linked list and add nodes
cll = CircularLinkedList()
print("Adding nodes to the end of circular linked list:")

cll.add_at_end(21)
print("After adding 21:")
cll.print_list()

cll.add_at_end(53)
print("\nAfter adding 53:")
cll.print_list()

cll.add_at_end(76)
print("\nAfter adding 76:")
cll.print_list()

Adding nodes to the end of circular linked list:
After adding 21:
21 -> (back to head)

After adding 53:
21 -> 53 -> (back to head)

After adding 76:
21 -> 53 -> 76 -> (back to head)

How It Works

The insertion process follows these steps:

1. Empty List: If the list is empty, the new node becomes both head and tail, pointing to itself
2. Non-empty List: The current tail's next pointer is updated to point to the new node
3. Update Tail: The new node becomes the new tail
4. Maintain Circle: The new tail's next pointer is set to point back to the head

Key Features

• The Node class contains data and a next pointer
• The CircularLinkedList class maintains head and tail pointers
• The add_at_end() method handles both empty and non-empty list cases
• The circular structure is maintained by always pointing the tail to the head

Conclusion

Inserting at the end of a circular linked list requires updating the tail pointer and maintaining the circular connection to the head. This operation has O(1) time complexity when a tail pointer is maintained.