Circular Linked List | Set 2 (Traversal)

We have discussed Circular Linked List Introduction and Applications, in the previous post on Circular Linked List. In this post, traversal operation is discussed. 

In a conventional linked list, we traverse the list from the head node and stop the traversal when we reach NULL. In a circular linked list, we stop traversal when we reach the first node again. Following is the C code for the linked list traversal.  

C++

/* Function to print nodes in
a given Circular linked list */
void printList(Node* head)
{
    Node* temp = head;

    // If linked list is not empty
    if (head != NULL) {

        // Print nodes till we reach first node again
        do {
            cout << temp->data << " ";
            temp = temp->next;
        } while (temp != head);
    }
}

C

/* Function to traverse a given Circular linked list and print nodes */
void printList(struct Node *first)
{
    struct Node *temp = first;

    // If linked list is not empty
    if (first != NULL)
    {
        // Keep printing nodes till we reach the first node again
        do
        {
            printf("%d ", temp->data);
            temp = temp->next;
        }
        while (temp != first);
    }
}

Java

/* Function to print nodes in a
given Circular linked list */
static void printList(Node head)
{
    Node temp = head;

    // If linked list is not empty
    if (head != null)
    {

        // Keep printing nodes till we reach the first node
        // again
        do
        {
            System.out.print(temp.data + " ");
            temp = temp.next;
        } while (temp != head);
    }
}

// This code is contributed by pratham76.

Python3

# Function to print nodes in a given Circular linked list
def printList(self):

    temp = self.head

    # If linked list is not empty
    if self.head is not None:
        while(True):

            # Print nodes till we reach first node again
            print(temp.data, end=" ")
            temp = temp.next
            if (temp == self.head):
                break

C#

/* Function to print nodes in a
given Circular linked list */
static void printList(Node head)
{
    Node temp = head;

    // If linked list is not empty
    if (head != null) {

        // Keep printing nodes till we reach the first node
        // again
        do {
            Console.Write(temp.data + " ");
            temp = temp.next;
        } while (temp != head);
    }
}

//This code is contributed by rutvik_56

Javascript

<script>
/* Function to print nodes in a
given Circular linked list */
function printList(head)
{
    var temp = head;

    // If linked list is not empty
    if (head != null)
    {

        // Keep printing nodes till we reach the first node
        // again
        do
        {
            document.write(temp.data + " ");
            temp = temp.next;
        } while (temp != head);
    }
}


// This code contributed by umadevi9616
</script>

Time Complexity: O(n)

Auxiliary Space: O(1)

Complete program to demonstrate traversal. Following are complete programs to demonstrate traversal of circular linked list.  

C++

// C++ program to implement
// the above approach
#include <bits/stdc++.h>
using namespace std;

/* structure for a node */
class Node
{
    public:
    int data;
    Node *next;
};

/* Function to insert a node at the beginning
of a Circular linked list */
void push(Node **head_ref, int data)
{
    Node *ptr1 = new Node();
    Node *temp = *head_ref;
    ptr1->data = data;
    ptr1->next = *head_ref;

    /* If linked list is not NULL then
    set the next of last node */
    if (*head_ref != NULL)
    {
        while (temp->next != *head_ref)
            temp = temp->next;
        temp->next = ptr1;
    }
    else
        ptr1->next = ptr1; /*For the first node */

    *head_ref = ptr1;
}

/* Function to print nodes in
a given Circular linked list */
void printList(Node *head)
{
    Node *temp = head;
    if (head != NULL)
    {
        do
        {
            cout << temp->data << " ";
            temp = temp->next;
        }
        while (temp != head);
    }
}

/* Driver program to test above functions */
int main()
{
    /* Initialize lists as empty */
    Node *head = NULL;

    /* Created linked list will be 11->2->56->12 */
    push(&head, 12);
    push(&head, 56);
    push(&head, 2);
    push(&head, 11);

    cout << "Contents of Circular Linked List\n ";
    printList(head);

    return 0;
}

C

// C program to implement
// the above approach
#include<stdio.h>
#include<stdlib.h>

/* structure for a node */
struct Node
{
    int data;
    struct Node *next;
};

/* Function to insert a node at the beginning of a Circular
   linked list */
void push(struct Node **head_ref, int data)
{
    struct Node *ptr1 = (struct Node *)malloc(sizeof(struct Node));
    struct Node *temp = *head_ref;
    ptr1->data = data;
    ptr1->next = *head_ref;

    /* If linked list is not NULL then set the next of last node */
    if (*head_ref != NULL)
    {
        while (temp->next != *head_ref)
            temp = temp->next;
        temp->next = ptr1;
    }
    else
        ptr1->next = ptr1; /*For the first node */

    *head_ref = ptr1;
}

/* Function to print nodes in a given Circular linked list */
void printList(struct Node *head)
{
    struct Node *temp = head;
    if (head != NULL)
    {
        do
        {
            printf("%d ", temp->data);
            temp = temp->next;
        }
        while (temp != head);
    }
}

/* Driver program to test above functions */
int main()
{
    /* Initialize lists as empty */
    struct Node *head = NULL;

    /* Created linked list will be 11->2->56->12 */
    push(&head, 12);
    push(&head, 56);
    push(&head, 2);
    push(&head, 11);

    printf("Contents of Circular Linked List\n ");
    printList(head);

    return 0;
}

Java

// Java program to implement
// the above approach
class GFG {

    // node
    static class Node {
        int data;
        Node next;
    };

    /* Function to insert a node
    at the beginning of a Circular
    linked list */
    static Node push(Node head_ref, int data)
    {
        Node ptr1 = new Node();
        Node temp = head_ref;
        ptr1.data = data;
        ptr1.next = head_ref;

        /* If linked list is not null
        then set the next of last node */
        if (head_ref != null) {
            while (temp.next != head_ref)
                temp = temp.next;
            temp.next = ptr1;
        }
        else
            ptr1.next = ptr1;

        head_ref = ptr1;

        return head_ref;
    }

    /* Function to print nodes in a
    given Circular linked list */
    static void printList(Node head)
    {
        Node temp = head;
        if (head != null) {
            do {
                System.out.print(temp.data + " ");
                temp = temp.next;
            } while (temp != head);
        }
    }

    // Driver Code
    public static void main(String args[])
    {
        /* Initialize lists as empty */
        Node head = null;

        /* Created linked list will
           be 11.2.56.12 */
        head = push(head, 12);
        head = push(head, 56);
        head = push(head, 2);
        head = push(head, 11);

        System.out.println("Contents of Circular "
                           + "Linked List:");
        printList(head);
    }
}

Python3

# Python program to demonstrate
# circular linked list traversal

# Structure for a Node
class Node:

    # Constructor to create  a new node
    def __init__(self, data):
        self.data = data
        self.next = None

class CircularLinkedList:

    # Constructor to create a empty circular linked list
    def __init__(self):
        self.head = None

    # Function to insert a node at the beginning of a
    # circular linked list
    def push(self, data):
        ptr1 = Node(data)
        temp = self.head

        ptr1.next = self.head

        # If linked list is not None then set the next of
        # last node
        if self.head is not None:
            while(temp.next != self.head):
                temp = temp.next
            temp.next = ptr1

        else:
            ptr1.next = ptr1 # For the first node

        self.head = ptr1

    # Function to print nodes in a given circular linked list
    def printList(self):
        temp = self.head
        if self.head is not None:
            while(True):
                print (temp.data, end=" ")
                temp = temp.next
                if (temp == self.head):
                    break


# Driver program to test above function

# Initialize list as empty
cllist = CircularLinkedList()

# Created linked list will be 11->2->56->12
cllist.push(12)
cllist.push(56)
cllist.push(2)
cllist.push(11)

print ("Contents of circular Linked List")
cllist.printList()

C#

// C# program to implement
// the above approach
using System;
class GFG
{

// node
class Node
{
    public int data;
    public Node next;
};

/* Function to insert a node
at the beginning of a Circular
linked list */
static Node push(Node head_ref,
                int data)
{
    Node ptr1 = new Node();
    Node temp = head_ref;
    ptr1.data = data;
    ptr1.next = head_ref;

    /* If linked list is not null
    then set the next of last node */
    if (head_ref != null)
    {
        while (temp.next != head_ref)
            temp = temp.next;
        temp.next = ptr1;
    }
    else
        ptr1.next = ptr1;

    head_ref = ptr1;

    return head_ref;
}

/* Function to print nodes in a
given Circular linked list */
static void printList(Node head)
{
    Node temp = head;
    if (head != null)
    {
        do
        {
            Console.Write(temp.data + " ");
            temp = temp.next;
        }
        while (temp != head);
    }
}

// Driver Code
static public void Main(String []args)
{
    /* Initialize lists as empty */
    Node head = null;

    /* Created linked list will
    be 11.2.56.12 */
    head = push(head, 12);
    head = push(head, 56);
    head = push(head, 2);
    head = push(head, 11);

    Console.WriteLine("Contents of Circular " +
                                "Linked List:");
    printList(head);
}
}

Javascript

<script>

// JavaScript program to implement
// the above approach

// node
class Node
{
    constructor(data)
    {
        this.data=data;
        this.next=null;
    }
}

/* Function to insert a node
at the beginning of a Circular
linked list */
function push(head_ref, data)
{
    let ptr1 = new Node();
    let temp = head_ref;
    ptr1.data = data;
    ptr1.next = head_ref;

    /* If linked list is not null
    then set the next of last node */
    if (head_ref != null)
    {
        while (temp.next != head_ref)
            temp = temp.next;
        temp.next = ptr1;
    }
    else
        ptr1.next = ptr1;

    head_ref = ptr1;

    return head_ref;
}

/* Function to print nodes in a
given Circular linked list */
function printList(head)
{
    let temp = head;
    if (head != null)
    {
        do
        {
            document.write(temp.data + " ");
            temp = temp.next;
        }
        while (temp != head);
    }
}

// Driver Code
/* Initialize lists as empty */
let head = null;

/* Created linked list will
       be 11.2.56.12 */
head = push(head, 12);
head = push(head, 56);
head = push(head, 2);
head = push(head, 11);

document.write("Contents of Circular " +
                   "Linked List:<br>");
printList(head);


</script>

Output:

Contents of Circular Linked List
11 2 56 12

Time Complexity: O(n) As we need to move through the whole list, Auxiliary Space: O(1) As no extra space is used

Complete program to traverse a Circular linked list using recursion: Program to traverse linked list using recursion is as follows:

Python3

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


class CircularLinkedList:
    def __init__(self):
        self.head = None

    def push(self, data, temp=None):
        if self.head == None:
            node = Node(data)
            self.head = node
            node.next = self.head
            return

        if temp == None:
            temp = self.head

        if temp.next == self.head:
            node = Node(data)
            node.next = self.head
            temp.next = node
            return

        self.push(data, temp.next)

    def traverse(self, temp=None):
        if temp == None:
            temp = self.head

        if temp.next == self.head:
            print(temp.data, end="\n")
            return
        print(temp.data, end="-->")
        self.traverse(temp.next)


if __name__ == "__main__":
    clist = CircularLinkedList()
    clist.push(2)
    clist.push(3)
    clist.push(7)
    clist.push(5)
    print("Traversed Circular Linked List: ", end="\n")
    clist.traverse()

Output

Traversed Circular Linked List: 
2-->3-->7-->5

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

You may like to see the following posts on Circular Linked List

Split a Circular Linked List into two halves
Sorted insert for circular linked list

We will soon be discussing the implementation of insert delete operations for circular linked lists.
Please write comments if you find any bug in the above code/algorithm, or find other ways to solve the same problem.