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Doubly Circular Linked List | Set 1 (Introduction and Insertion)
  • Difficulty Level : Easy
  • Last Updated : 22 Jun, 2021

Prerequisite: Doubly Linked list, Circular Linked List 
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 previous and next pointer and the last node points to first node by next pointer and also the first node points to last node by previous pointer.

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

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

 

Circular doubly linked list

Insertion in Circular Doubly Linked List
 



Insertion in Circular Doubly Linked List

  • Insertion at the end of list or in an empty list
    • Empty List (start = NULL): A node(Say N) is inserted with data = 5, so previous pointer of N points to N and next pointer of N also points to N. But now start pointer points to the first node the list.
       

Insertion in empty list1

  • List initially contain some nodes, start points to first node of the List: A node(Say M) is inserted with data = 7, so previous pointer of M points to last node, next pointer of M points to first node and last node’s next pointer points to this M node and first node’s previous pointer points to this M node.
     

Insertion in a list

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 preivous 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 preivous 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

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 preivous 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




<script>
// 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 preivous of new node
    new_node.prev = last;
  
    // Make new node next of old last
    last.next = new_node;
}
 
 
// This code contributed by aashish1995
</script>
  • 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 first node of the list, T previous pointer points to last node 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 beginning of list

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;
}
  • 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 the list

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;
}

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 Cicular 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 preivous 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 Cicular 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 preivous 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 Cicular Doubly Linked list
# in begging, end and middle
start = None
 
# 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 preivous 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 Cicular 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 preivous 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




<script>
 
      // JavaScript program to illustrate inserting a Node in
      // a Cicular 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 preivous 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();
       
</script>

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

Following are advantages and disadvantages of circular doubly linked list: 
Advantages: 

  • List can be traversed from both the 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 implementation of advanced data structures like Fibonacci Heap.

Disadvantages 

  • It takes slightly extra memory in each node to accommodate previous pointer.
  • Lots of pointers 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 songs playlist in media player applications.
  • Managing shopping cart 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.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 

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