Insertion at the end in circular linked list

Last Updated : 08 Aug, 2024

A circular linked list is a data structure where each node points to the next, and the last node connects back to the first, creating a loop. Insertion at the end in circular linked list is an important operation. Understanding how to perform this insertion is essential for effectively manage and use circular linked lists in various applications.

Insertion at the end in circular linked list

To insert a new node at the end of a circular linked list, we first create the new node and allocate memory for it. If the list is empty (mean, last or tail pointer being NULL), we initialize the list with the new node and making it point to itself to form a circular structure. If the list already contains nodes then we set the new node’s next pointer to point to the current head (which is tail->next), then update the current tail's next pointer to point to the new node. Finally, we update the tail pointer to the new node. This will ensure that the new node is now the last node in the list while maintaining the circular linkage.

Insertion-at-the-end-of-circular-linked-list — Insertion at the end in circular linked list

Step-by-step approach:

Create a new node with the given value.
Check Empty List, If last is nullptr then initialize the list with the new node and make it point to itself.
Otherwise, Set the new node's next to the head node.
Update the current last's next to point to the new node.
Update last to the new node.

Below is the implementation of the above approach:

C++

#include <iostream> using namespace std;  struct Node{     int data;     Node *next;     Node(int value)     {         data = value;         next = nullptr;     } };  // Function to insert a node at the end of a circular linked list Node *insertEnd(Node *tail, int value) {     Node *newNode = new Node(value);     if (tail == nullptr){         // If the list is empty, initialize it with the new node         tail = newNode;          // Point to itself to form a circular structure         newNode->next = newNode;     }     else{         // Insert new node after the current tail         // and update the tail pointer.         // New node points to the head node         newNode->next = tail->next;          // Tail node points to the new node         tail->next = newNode;          // Update tail to be the new node         tail = newNode;     }     return tail; }  void printList(Node *last){   if(last == NULL) return;        // Start from the head node     Node *head = last->next;     while (true){         cout << head->data << " ";         head = head->next;         if (head == last->next)             break;     }     cout << endl; }  int main(){     // Create circular linked list: 2, 3, 4     Node *first = new Node(2);     first->next = new Node(3);     first->next->next = new Node(4);      Node *last = first->next->next;     last->next = first;      cout << "Original list: ";     printList(last);      // Insert elements at the end of the circular linked list     last = insertEnd(last, 5);     last = insertEnd(last, 6);      cout << "List after inserting 5 and 6: ";     printList(last);      return 0; }

#include <stdio.h> #include <stdlib.h>  // Define the Node structure struct Node {     int data;     struct Node *next; };  // Function to create a new node struct Node *createNode(int value);  // Function to insert a node at the end of a circular linked list struct Node *insertEnd(struct Node *tail, int value) {     struct Node *newNode = createNode(value);     if (tail == NULL)     {         // If the list is empty, initialize it with the new node         tail = newNode;         newNode->next = newNode;     }     else     {         // Insert new node after the current tail and update the tail pointer         newNode->next = tail->next;         tail->next = newNode;         tail = newNode;     }     return tail; }  // Function to print the circular linked list void printList(struct Node *last) {     if (last == NULL)         return;      struct Node *head = last->next;     while (1)     {         printf("%d ", head->data);         head = head->next;         if (head == last->next)             break;     }     printf("\n"); }  struct Node *createNode(int value) {     struct Node *newNode = (struct Node *)malloc(sizeof(struct Node));     newNode->data = value;     newNode->next = NULL;     return newNode; }  int main() {     // Create circular linked list: 2, 3, 4     struct Node *first = createNode(2);     first->next = createNode(3);     first->next->next = createNode(4);      struct Node *last = first->next->next;     last->next = first;      printf("Original list: ");     printList(last);      // Insert elements at the end of the circular linked list     last = insertEnd(last, 5);     last = insertEnd(last, 6);      printf("List after inserting 5 and 6: ");     printList(last);      return 0; }

Java

class Node {     int data;     Node next;      Node(int value){         data = value;         next = null;     } }  public class GFG {      // Function to insert a node at the end of a circular     // linked list     static Node insertEnd(Node tail, int value){         Node newNode = new Node(value);         if (tail == null) {             // If the list is empty, initialize it with the             // new node             tail = newNode;             newNode.next = newNode;         }         else {             // Insert new node after the current tail and             // update the tail pointer             newNode.next = tail.next;             tail.next = newNode;             tail = newNode;         }         return tail;     }      // Function to print the circular linked list     static void printList(Node last){         if (last == null) return;          Node head = last.next;         while (true) {             System.out.print(head.data + " ");             head = head.next;             if (head == last.next) break;         }         System.out.println();     }      public static void main(String[] args){         // Create circular linked list: 2, 3, 4         Node first = new Node(2);         first.next = new Node(3);         first.next.next = new Node(4);          Node last = first.next.next;         last.next = first;          System.out.print("Original list: ");         printList(last);          // Insert elements at the end of the circular linked         // list         last = insertEnd(last, 5);         last = insertEnd(last, 6);          System.out.print("List after inserting 5 and 6: ");         printList(last);     } }

Python

class Node:     def __init__(self, value):         self.data = value         self.next = None  # Function to insert a node at the end of a circular linked list   def insert_end(tail, value):     new_node = Node(value)     if tail is None:         # If the list is empty, initialize         # it with the new node         tail = new_node         new_node.next = new_node     else:         # Insert new node after the current tail         # and update the tail pointer         new_node.next = tail.next         tail.next = new_node         tail = new_node     return tail  # Function to print the circular linked list   def print_list(last):     if last is None:         return      head = last.next     while True:         print(head.data, end=" ")         head = head.next         if head == last.next:             break     print()   if __name__ == "__main__":     # Create circular linked list: 2, 3, 4     first = Node(2)     first.next = Node(3)     first.next.next = Node(4)      last = first.next.next     last.next = first      print("Original list: ", end="")     print_list(last)      # Insert elements at the end of the circular linked list     last = insert_end(last, 5)     last = insert_end(last, 6)      print("List after inserting 5 and 6: ", end="")     print_list(last)

JavaScript

class Node {     constructor(value){         this.data = value;         this.next = null;     } }  // Function to insert a node at the end of a circular linked // list function insertEnd(tail, value){     let newNode = new Node(value);     if (tail === null) {         // If the list is empty, initialize it with the new         // node         tail = newNode;         newNode.next = newNode;     }     else {         // Insert new node after the current tail and update         // the tail pointer         newNode.next = tail.next;         tail.next = newNode;         tail = newNode;     }     return tail; }  // Function to print the circular linked list function printList(last) {     if (last === null)         return;      let head = last.next;     while (true) {         console.log(head.data + " ");         head = head.next;         if (head === last.next)             break;     }     console.log(); }  // Create circular linked list: 2, 3, 4 let first = new Node(2); first.next = new Node(3); first.next.next = new Node(4);  let last = first.next.next; last.next = first;  console.log("Original list: "); printList(last);  // Insert elements at the end of the circular linked // list last = insertEnd(last, 5); last = insertEnd(last, 6);  console.log("List after inserting 5 and 6: "); printList(last);

Output

Original list: 2 3 4  List after inserting 5 and 6: 2 3 4 5 6

Time Complexity: O(1)
Auxiliary Space: O(1)

Insertion in an empty List in the circular linked list

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Insertion at the end in circular linked list

Insertion at the end in circular linked list

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