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Insertion in Doubly Circular Linked List

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  • Difficulty Level : Easy
  • Last Updated : 02 Nov, 2022
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Circular Doubly Linked List has properties of both doubly linked list and circular linked list in which two consecutive elements are linked or connected by the previous and next pointer and the last node points to the first node by the next pointer and also the first node points to the last node by the previous pointer.

Following is the representation of a Circular doubly linked list node in C/C++: 

C




// Structure of the node
struct node {
    int data;
  
    // Pointer to next node
    struct node* next;
  
    // Pointer to previous node
    struct node* prev;
};


 

Circular Doubly Linked LIst

Circular Doubly Linked LIst

Insertion in Circular Doubly Linked List:

1. Insertion at the end of the list or in an empty list:

A node(Say N) is inserted with data = 5. So, the previous pointer of N points to N and the next pointer of N also points to N. But now start pointer points to the first node of the list.

Insertion in an empty list

Insertion in an empty list

2. List initially contains some nodes, start points to the first node of the List: 

A node(Say M) is inserted with data = 7, so the previous pointer of M points to the last node, the next pointer of M points to the first node and the last node’s next pointer points to this M node, and first node’s previous pointer points to this M node.

Insertion at the end of list

Insertion at the end of list

Below is the implementation of the above operations:

C++




// Function to insert at the end
void insertEnd(struct Node** start, int value)
{
    // If the list is empty, create a single node
    // circular and doubly list
    if (*start == NULL) {
        struct Node* new_node = new Node;
        new_node->data = value;
        new_node->next = new_node->prev = new_node;
        *start = new_node;
        return;
    }
  
    // If list is not empty
  
    /* Find last node */
    Node* last = (*start)->prev;
  
    // Create Node dynamically
    struct Node* new_node = new Node;
    new_node->data = value;
  
    // Start is going to be next of new_node
    new_node->next = *start;
  
    // Make new node previous of start
    (*start)->prev = new_node;
  
    // Make last previous of new node
    new_node->prev = last;
  
    // Make new node next of old last
    last->next = new_node;
}


Java




// Function to insert at the end
static void insertEnd(int value)
{
  
    // If the list is empty, create a single
    // node circular and doubly list
    if (start == null) {
        Node new_node = new Node();
        new_node.data = value;
        new_node.next = new_node.prev = new_node;
        start = new_node;
        return;
    }
  
    // If list is not empty
  
    // Find last node
    Node last = (start).prev;
  
    // Create Node dynamically
    Node new_node = new Node();
    new_node.data = value;
  
    // Start is going to be
    // next of new_node
    new_node.next = start;
  
    // Make new node previous of start
    (start).prev = new_node;
  
    // Make last previous of new node
    new_node.prev = last;
  
    // Make new node next of old last
    last.next = new_node;
}
  
// This code is contributed by rutvik_56


Python3




# Function to insert at the end
def insertEnd(value):
    global start
  
    # If the list is empty, create a
    # single node circular and doubly list
    if (start == None):
  
        new_node = Node(0)
        new_node.data = value
        new_node.next = new_node.prev = new_node
        start = new_node
        return
  
    # If list is not empty
  
    # Find last node */
    last = (start).prev
  
    # Create Node dynamically
    new_node = Node(0)
    new_node.data = value
  
    # Start is going to be next of new_node
    new_node.next = start
  
    # Make new node previous of start
    (start).prev = new_node
  
    # Make last previous of new node
    new_node.prev = last
  
    # Make new node next of old last
    last.next = new_node
  
    # This code is contributed by shivanisinghss2110


C#




// Function to insert at the end
static void insertEnd(int value)
{
    Node new_node;
  
    // If the list is empty, create a single node
    // circular and doubly list
    if (start == null) {
        new_node = new Node();
        new_node.data = value;
        new_node.next = new_node.prev = new_node;
        start = new_node;
        return;
    }
  
    // If list is not empty
  
    /* Find last node */
    Node last = (start).prev;
  
    // Create Node dynamically
    new_node = new Node();
    new_node.data = value;
  
    // Start is going to be next of new_node
    new_node.next = start;
  
    // Make new node previous of start
    (start).prev = new_node;
  
    // Make last previous of new node
    new_node.prev = last;
  
    // Make new node next of old last
    last.next = new_node;
}
  
// This code is contributed by Pratham76


Javascript




// Function to insert at the end 
function insertEnd(value) 
      
    // If the list is empty, create a single
      // node circular and doubly list 
    if (start == null
    
        var new_node = new Node(); 
        new_node.data = value; 
        new_node.next = new_node.prev = new_node; 
        start = new_node; 
        return
    
   
    // If list is not empty 
   
    // Find last node 
    var last = (start).prev; 
   
    // Create Node dynamically 
    var new_node = new Node(); 
    new_node.data = value; 
   
    // Start is going to be 
      // next of new_node 
    new_node.next = start; 
   
    // Make new node previous of start 
    (start).prev = new_node; 
   
    // Make last previous of new node 
    new_node.prev = last; 
   
    // Make new node next of old last 
    last.next = new_node; 
  
  
// This code contributed by aashish1995 


3. Insertion at the beginning of the list: 

To insert a node at the beginning of the list, create a node(Say T) with data = 5, T next pointer points to the first node of the list, T previous pointer points to the last node of the list, last node’s next pointer points to this T node, first node’s previous pointer also points this T node and at last don’t forget to shift ‘Start’ pointer to this T node.

Insertion at the beginning of the list

Insertion at the beginning of the list

Below is the implementation of the above operation:

C++




// Function to insert Node at the beginning
// of the List,
void insertBegin(struct Node** start, int value)
{
    // Pointer points to last Node
    struct Node* last = (*start)->prev;
  
    struct Node* new_node = new Node;
    new_node->data = value; // Inserting the data
  
    // setting up previous and next of new node
    new_node->next = *start;
    new_node->prev = last;
  
    // Update next and previous pointers of start
    // and last.
    last->next = (*start)->prev = new_node;
  
    // Update start pointer
    *start = new_node;
}


Java




// Function to insert Node at the beginning
// of the List,
static void insertBegin(int value)
{
    // Pointer points to last Node
    Node last = (start).prev;
  
    Node new_node = new Node();
    new_node.data = value; // Inserting the data
  
    // setting up previous and next of new node
    new_node.next = start;
    new_node.prev = last;
  
    // Update next and previous pointers of start
    // and last.
    last.next = (start).prev = new_node;
  
    // Update start pointer
    start = new_node;
}
  
// this code is contributed by shivanisinghss2110


Python3




# Function to insert Node at the beginning
# of the List,
  
  
def insertBegin(value):
    global start
  
    # Pointer points to last Node
    last = (start).prev
  
    new_node = Node(0)
    new_node.data = value  # Inserting the data
  
    # setting up previous and
    # next of new node
    new_node.next = start
    new_node.prev = last
  
    # Update next and previous pointers
    # of start and last.
    last.next = (start).prev = new_node
  
    # Update start pointer
    start = new_node
  
    # This code is contributed by shivanisinghss2110


C#




// Function to insert Node at the beginning
// of the List,
static void insertBegin(int value)
{
  
    // Pointer points to last Node
    Node last = (start).prev;
  
    Node new_node = new Node();
    new_node.data = value; // Inserting the data
  
    // setting up previous and next of new node
    new_node.next = start;
    new_node.prev = last;
  
    // Update next and previous pointers of start
    // and last.
    last.next = (start).prev = new_node;
  
    // Update start pointer
    start = new_node;
}
  
// This code is contributed by shivanisinghss2110


Javascript




// Function to insert Node at the beginning
      // of the List,
      function insertBegin(value) {
        // Pointer points to last Node
        var last = start.prev;
  
        var new_node = new Node();
        new_node.data = value; // Inserting the data
  
        // setting up previous and next of new node
        new_node.next = start;
        new_node.prev = last;
  
        // Update next and previous pointers of start
        // and last.
        last.next = start.prev = new_node;
  
        // Update start pointer
        start = new_node;
      }
        
      // This code is contributed by shivanisinghss2110


4. Insertion in between the nodes of the list

To insert a node in between the list, two data values are required one after which new node will be inserted and another is the data of the new node.

Insertion in between other nodes

Insertion in between other nodes

Below is the implementation of the above operation:

C++




// Function to insert node with value as value1.
// The new node is inserted after the node with
// with value2
void insertAfter(struct Node** start, int value1,
                 int value2)
{
    struct Node* new_node = new Node;
    new_node->data = value1; // Inserting the data
  
    // Find node having value2 and next node of it
    struct Node* temp = *start;
    while (temp->data != value2)
        temp = temp->next;
    struct Node* next = temp->next;
  
    // insert new_node between temp and next.
    temp->next = new_node;
    new_node->prev = temp;
    new_node->next = next;
    next->prev = new_node;
}


Java




// Function to insert node with value as value1.
// The new node is inserted after the node with
// with value2
static void insertAfter(int value1, int value2)
{
    Node new_node = new Node();
    new_node.data = value1; // Inserting the data
  
    // Find node having value2 and next node of it
    Node temp = start;
    while (temp.data != value2)
        temp = temp.next;
    Node next = temp.next;
  
    // insert new_node between temp and next.
    temp.next = new_node;
    new_node.prev = temp;
    new_node.next = next;
    next.prev = new_node;
}
  
// this code is contributed by shivanisinghss2110


Python3




# Function to insert node with value as value1.
# The new node is inserted after the node with
# with value2
  
  
def insertAfter(value1, value2):
    global start
    new_node = Node(0)
    new_node.data = value1  # Inserting the data
  
    # Find node having value2 and
    # next node of it
    temp = start
    while (temp.data != value2):
        temp = temp.next
    next = temp.next
  
    # insert new_node between temp and next.
    temp.next = new_node
    new_node.prev = temp
    new_node.next = next
    next.prev = new_node
  
# this code is contributed by shivanisinghss2110


C#




// Function to insert node with value as value1.
// The new node is inserted after the node with
// with value2
static void insertAfter(int value1, int value2)
{
    Node new_node = new Node();
    new_node.data = value1; // Inserting the data
  
    // Find node having value2 and next node of it
    Node temp = start;
    while (temp.data != value2)
        temp = temp.next;
    Node next = temp.next;
  
    // insert new_node between temp and next.
    temp.next = new_node;
    new_node.prev = temp;
    new_node.next = next;
    next.prev = new_node;
}
  
// this code is contributed by shivanisinghss2110


Javascript




<script>
  
// Function to insert node with value as value1.
// The new node is inserted after the node with
// with value2
function insertAfter(value1, value2) 
{
    var new_node = new Node();
      
    // Inserting the data
    new_node.data = value1; 
  
    // Find node having value2 and
    // next node of it
    var temp = start;
    while (temp.data != value2) 
        temp = temp.next;
          
    var next = temp.next;
  
    // Insert new_node between temp and next.
    temp.next = new_node;
    new_node.prev = temp;
    new_node.next = next;
    next.prev = new_node;
}
        
// This code is contributed by shivanisinghss2110
  
</script>


Following is a complete program that uses all of the above methods to create a circular doubly linked list.  

C++




// C++ program to illustrate inserting a Node in
// a Circular Doubly Linked list in begging, end
// and middle
#include <bits/stdc++.h>
using namespace std;
  
// Structure of a Node
struct Node {
    int data;
    struct Node* next;
    struct Node* prev;
};
  
// Function to insert at the end
void insertEnd(struct Node** start, int value)
{
    // If the list is empty, create a single node
    // circular and doubly list
    if (*start == NULL) {
        struct Node* new_node = new Node;
        new_node->data = value;
        new_node->next = new_node->prev = new_node;
        *start = new_node;
        return;
    }
  
    // If list is not empty
  
    /* Find last node */
    Node* last = (*start)->prev;
  
    // Create Node dynamically
    struct Node* new_node = new Node;
    new_node->data = value;
  
    // Start is going to be next of new_node
    new_node->next = *start;
  
    // Make new node previous of start
    (*start)->prev = new_node;
  
    // Make last previous of new node
    new_node->prev = last;
  
    // Make new node next of old last
    last->next = new_node;
}
  
// Function to insert Node at the beginning
// of the List,
void insertBegin(struct Node** start, int value)
{
    // Pointer points to last Node
    struct Node* last = (*start)->prev;
  
    struct Node* new_node = new Node;
    new_node->data = value; // Inserting the data
  
    // setting up previous and next of new node
    new_node->next = *start;
    new_node->prev = last;
  
    // Update next and previous pointers of start
    // and last.
    last->next = (*start)->prev = new_node;
  
    // Update start pointer
    *start = new_node;
}
  
// Function to insert node with value as value1.
// The new node is inserted after the node with
// with value2
void insertAfter(struct Node** start, int value1,
                 int value2)
{
    struct Node* new_node = new Node;
    new_node->data = value1; // Inserting the data
  
    // Find node having value2 and next node of it
    struct Node* temp = *start;
    while (temp->data != value2)
        temp = temp->next;
    struct Node* next = temp->next;
  
    // insert new_node between temp and next.
    temp->next = new_node;
    new_node->prev = temp;
    new_node->next = next;
    next->prev = new_node;
}
  
void display(struct Node* start)
{
    struct Node* temp = start;
  
    printf("\nTraversal in forward direction \n");
    while (temp->next != start) {
        printf("%d ", temp->data);
        temp = temp->next;
    }
    printf("%d ", temp->data);
  
    printf("\nTraversal in reverse direction \n");
    Node* last = start->prev;
    temp = last;
    while (temp->prev != last) {
        printf("%d ", temp->data);
        temp = temp->prev;
    }
    printf("%d ", temp->data);
}
  
/* Driver program to test above functions*/
int main()
{
    /* Start with the empty list */
    struct Node* start = NULL;
  
    // Insert 5. So linked list becomes 5->NULL
    insertEnd(&start, 5);
  
    // Insert 4 at the beginning. So linked
    // list becomes 4->5
    insertBegin(&start, 4);
  
    // Insert 7 at the end. So linked list
    // becomes 4->5->7
    insertEnd(&start, 7);
  
    // Insert 8 at the end. So linked list
    // becomes 4->5->7->8
    insertEnd(&start, 8);
  
    // Insert 6, after 5. So linked list
    // becomes 4->5->6->7->8
    insertAfter(&start, 6, 5);
  
    printf("Created circular doubly linked list is: ");
    display(start);
  
    return 0;
}


Java




// Java program to illustrate inserting a Node in
// a Circular Doubly Linked list in begging, end
// and middle
import java.util.*;
  
class GFG {
  
    static Node start;
  
    // Structure of a Node
    static class Node {
        int data;
        Node next;
        Node prev;
    };
  
    // Function to insert at the end
    static void insertEnd(int value)
    {
        // If the list is empty, create a single node
        // circular and doubly list
        if (start == null) {
            Node new_node = new Node();
            new_node.data = value;
            new_node.next = new_node.prev = new_node;
            start = new_node;
            return;
        }
  
        // If list is not empty
  
        /* Find last node */
        Node last = (start).prev;
  
        // Create Node dynamically
        Node new_node = new Node();
        new_node.data = value;
  
        // Start is going to be next of new_node
        new_node.next = start;
  
        // Make new node previous of start
        (start).prev = new_node;
  
        // Make last previous of new node
        new_node.prev = last;
  
        // Make new node next of old last
        last.next = new_node;
    }
  
    // Function to insert Node at the beginning
    // of the List,
    static void insertBegin(int value)
    {
        // Pointer points to last Node
        Node last = (start).prev;
  
        Node new_node = new Node();
        new_node.data = value; // Inserting the data
  
        // setting up previous and next of new node
        new_node.next = start;
        new_node.prev = last;
  
        // Update next and previous pointers of start
        // and last.
        last.next = (start).prev = new_node;
  
        // Update start pointer
        start = new_node;
    }
  
    // Function to insert node with value as value1.
    // The new node is inserted after the node with
    // with value2
    static void insertAfter(int value1, int value2)
    {
        Node new_node = new Node();
        new_node.data = value1; // Inserting the data
  
        // Find node having value2 and next node of it
        Node temp = start;
        while (temp.data != value2)
            temp = temp.next;
        Node next = temp.next;
  
        // insert new_node between temp and next.
        temp.next = new_node;
        new_node.prev = temp;
        new_node.next = next;
        next.prev = new_node;
    }
  
    static void display()
    {
        Node temp = start;
  
        System.out.printf(
            "\nTraversal in forward direction \n");
        while (temp.next != start) {
            System.out.printf("%d ", temp.data);
            temp = temp.next;
        }
        System.out.printf("%d ", temp.data);
  
        System.out.printf(
            "\nTraversal in reverse direction \n");
        Node last = start.prev;
        temp = last;
        while (temp.prev != last) {
            System.out.printf("%d ", temp.data);
            temp = temp.prev;
        }
        System.out.printf("%d ", temp.data);
    }
  
    /* Driver code*/
    public static void main(String[] args)
    {
        /* Start with the empty list */
        Node start = null;
  
        // Insert 5. So linked list becomes 5.null
        insertEnd(5);
  
        // Insert 4 at the beginning. So linked
        // list becomes 4.5
        insertBegin(4);
  
        // Insert 7 at the end. So linked list
        // becomes 4.5.7
        insertEnd(7);
  
        // Insert 8 at the end. So linked list
        // becomes 4.5.7.8
        insertEnd(8);
  
        // Insert 6, after 5. So linked list
        // becomes 4.5.6.7.8
        insertAfter(6, 5);
  
        System.out.printf(
            "Created circular doubly linked list is: ");
        display();
    }
}
  
// This code is contributed by Rajput-Ji


Python3




# Python3 program to illustrate inserting
# a Node in a Circular Doubly Linked list
# in begging, end and middle
  
# Structure of a Node
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
        self.prev = None
  
# Function to insert at the end
  
  
def insertEnd(value):
    global start
  
    # If the list is empty, create a
    # single node circular and doubly list
    if (start == None):
  
        new_node = Node(0)
        new_node.data = value
        new_node.next = new_node.prev = new_node
        start = new_node
        return
  
    # If list is not empty
  
    # Find last node */
    last = (start).prev
  
    # Create Node dynamically
    new_node = Node(0)
    new_node.data = value
  
    # Start is going to be next of new_node
    new_node.next = start
  
    # Make new node previous of start
    (start).prev = new_node
  
    # Make last previous of new node
    new_node.prev = last
  
    # Make new node next of old last
    last.next = new_node
  
# Function to insert Node at the beginning
# of the List,
  
  
def insertBegin(value):
    global start
  
    # Pointer points to last Node
    last = (start).prev
  
    new_node = Node(0)
    new_node.data = value  # Inserting the data
  
    # setting up previous and
    # next of new node
    new_node.next = start
    new_node.prev = last
  
    # Update next and previous pointers
    # of start and last.
    last.next = (start).prev = new_node
  
    # Update start pointer
    start = new_node
  
# Function to insert node with value as value1.
# The new node is inserted after the node with
# with value2
  
  
def insertAfter(value1, value2):
    global start
    new_node = Node(0)
    new_node.data = value1  # Inserting the data
  
    # Find node having value2 and
    # next node of it
    temp = start
    while (temp.data != value2):
        temp = temp.next
    next = temp.next
  
    # insert new_node between temp and next.
    temp.next = new_node
    new_node.prev = temp
    new_node.next = next
    next.prev = new_node
  
  
def display():
    global start
    temp = start
  
    print("Traversal in forward direction:")
    while (temp.next != start):
  
        print(temp.data, end=" ")
        temp = temp.next
  
    print(temp.data)
  
    print("Traversal in reverse direction:")
    last = start.prev
    temp = last
    while (temp.prev != last):
  
        print(temp.data, end=" ")
        temp = temp.prev
  
    print(temp.data)
  
  
# Driver Code
if __name__ == '__main__':
    global start
  
    # Start with the empty list
    start = None
  
    # Insert 5. So linked list becomes 5.None
    insertEnd(5)
  
    # Insert 4 at the beginning. So linked
    # list becomes 4.5
    insertBegin(4)
  
    # Insert 7 at the end. So linked list
    # becomes 4.5.7
    insertEnd(7)
  
    # Insert 8 at the end. So linked list
    # becomes 4.5.7.8
    insertEnd(8)
  
    # Insert 6, after 5. So linked list
    # becomes 4.5.6.7.8
    insertAfter(6, 5)
  
    print("Created circular doubly linked list is: ")
    display()
  
# This code is contributed by Arnab kundu


C#




// C# program to illustrate inserting a Node in
// a Circular Doubly Linked list in begging, end
// and middle
using System;
using System.Collections.Generic;
  
class GFG {
    static Node start;
  
    // Structure of a Node
    public class Node {
        public int data;
        public Node next;
        public Node prev;
    };
  
    // Function to insert at the end
    static void insertEnd(int value)
    {
        Node new_node;
  
        // If the list is empty, create a single node
        // circular and doubly list
        if (start == null) {
            new_node = new Node();
            new_node.data = value;
            new_node.next = new_node.prev = new_node;
            start = new_node;
            return;
        }
  
        // If list is not empty
  
        /* Find last node */
        Node last = (start).prev;
  
        // Create Node dynamically
        new_node = new Node();
        new_node.data = value;
  
        // Start is going to be next of new_node
        new_node.next = start;
  
        // Make new node previous of start
        (start).prev = new_node;
  
        // Make last previous of new node
        new_node.prev = last;
  
        // Make new node next of old last
        last.next = new_node;
    }
  
    // Function to insert Node at the beginning
    // of the List,
    static void insertBegin(int value)
    {
        // Pointer points to last Node
        Node last = (start).prev;
  
        Node new_node = new Node();
        new_node.data = value; // Inserting the data
  
        // setting up previous and next of new node
        new_node.next = start;
        new_node.prev = last;
  
        // Update next and previous pointers of start
        // and last.
        last.next = (start).prev = new_node;
  
        // Update start pointer
        start = new_node;
    }
  
    // Function to insert node with value as value1.
    // The new node is inserted after the node with
    // with value2
    static void insertAfter(int value1, int value2)
    {
        Node new_node = new Node();
        new_node.data = value1; // Inserting the data
  
        // Find node having value2 and next node of it
        Node temp = start;
        while (temp.data != value2)
            temp = temp.next;
        Node next = temp.next;
  
        // insert new_node between temp and next.
        temp.next = new_node;
        new_node.prev = temp;
        new_node.next = next;
        next.prev = new_node;
    }
  
    static void display()
    {
        Node temp = start;
  
        Console.Write(
            "\nTraversal in forward direction \n");
        while (temp.next != start) {
            Console.Write("{0} ", temp.data);
            temp = temp.next;
        }
        Console.Write("{0} ", temp.data);
  
        Console.Write(
            "\nTraversal in reverse direction \n");
        Node last = start.prev;
        temp = last;
        while (temp.prev != last) {
            Console.Write("{0} ", temp.data);
            temp = temp.prev;
        }
        Console.Write("{0} ", temp.data);
    }
  
    /* Driver code*/
    public static void Main(String[] args)
    {
        /* Start with the empty list */
        Node start = null;
  
        // Insert 5. So linked list becomes 5.null
        insertEnd(5);
  
        // Insert 4 at the beginning. So linked
        // list becomes 4.5
        insertBegin(4);
  
        // Insert 7 at the end. So linked list
        // becomes 4.5.7
        insertEnd(7);
  
        // Insert 8 at the end. So linked list
        // becomes 4.5.7.8
        insertEnd(8);
  
        // Insert 6, after 5. So linked list
        // becomes 4.5.6.7.8
        insertAfter(6, 5);
  
        Console.Write(
            "Created circular doubly linked list is: ");
        display();
    }
}
  
// This code is contributed by Rajput-Ji


Javascript




// JavaScript program to illustrate inserting a Node in
// a Circular Doubly Linked list in begging, end
// and middle
var start = null;
 
// Structure of a Node
class Node {
  constructor() {
    this.data = 0;
    this.next = null;
    this.prev = null;
  }
}
 
// Function to insert at the end
function insertEnd(value) {
  var new_node;
 
  // If the list is empty, create a single node
  // circular and doubly list
  if (start == null) {
    new_node = new Node();
    new_node.data = value;
    new_node.next = new_node.prev = new_node;
    start = new_node;
    return;
  }
 
  // If list is not empty
 
  /* Find last node */
  var last = start.prev;
 
  // Create Node dynamically
  new_node = new Node();
  new_node.data = value;
 
  // Start is going to be next of new_node
  new_node.next = start;
 
  // Make new node previous of start
  start.prev = new_node;
 
  // Make last previous of new node
  new_node.prev = last;
 
  // Make new node next of old last
  last.next = new_node;
}
 
// Function to insert Node at the beginning
// of the List,
function insertBegin(value) {
  // Pointer points to last Node
  var last = start.prev;
 
  var new_node = new Node();
  new_node.data = value; // Inserting the data
 
  // setting up previous and next of new node
  new_node.next = start;
  new_node.prev = last;
 
  // Update next and previous pointers of start
  // and last.
  last.next = start.prev = new_node;
 
  // Update start pointer
  start = new_node;
}
 
// Function to insert node with value as value1.
// The new node is inserted after the node with
// with value2
function insertAfter(value1, value2) {
  var new_node = new Node();
  new_node.data = value1; // Inserting the data
 
  // Find node having value2 and next node of it
  var temp = start;
  while (temp.data != value2) temp = temp.next;
  var next = temp.next;
 
  // insert new_node between temp and next.
  temp.next = new_node;
  new_node.prev = temp;
  new_node.next = next;
  next.prev = new_node;
}
 
function display() {
  var temp = start;
 
  document.write("<br>Traversal in forward direction <br>");
  while (temp.next != start) {
    document.write(temp.data + " ");
    temp = temp.next;
  }
  document.write(temp.data);
 
  document.write("<br>Traversal in reverse direction <br>");
  var last = start.prev;
  temp = last;
  while (temp.prev != last) {
    document.write(temp.data + " ");
    temp = temp.prev;
  }
  document.write(temp.data);
}
 
/* Driver code*/
/* Start with the empty list */
var start = null;
 
// Insert 5. So linked list becomes 5.null
insertEnd(5);
 
// Insert 4 at the beginning. So linked
// list becomes 4.5
insertBegin(4);
 
// Insert 7 at the end. So linked list
// becomes 4.5.7
insertEnd(7);
 
// Insert 8 at the end. So linked list
// becomes 4.5.7.8
insertEnd(8);
 
// Insert 6, after 5. So linked list
// becomes 4.5.6.7.8
insertAfter(6, 5);
 
document.write("Created circular doubly linked list is: ");
display();


Output

Created circular doubly linked list is: 
Traversal in forward direction 
4 5 6 7 8 
Traversal in reverse direction 
8 7 6 5 4 

Time Complexity: O(N)
Auxiliary Space: O(1), As constant extra space is used.

Advantages of circular doubly linked list: 

  • The list can be traversed from both directions i.e. from head to tail or from tail to head.
  • Jumping from head to tail or from tail to head is done in constant time O(1).
  • Circular Doubly Linked Lists are used for the implementation of advanced data structures like the Fibonacci Heap.

Disadvantages of circular doubly linked list: 

  • It takes slightly extra memory in each node to accommodate the previous pointer.
  • Lots of pointers are involved while implementing or doing operations on a list. So, pointers should be handled carefully otherwise data of the list may get lost.

Applications of Circular doubly linked list:

  • Managing song playlists in media player applications.
  • Managing shopping carts in online shopping.

This article is contributed by Akash Gupta. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.


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