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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 C code for linked list traversal.

/* 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);
    }
}

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 begining 
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 "
    printList(head); 
  
    return 0; 
  
// This is code is contributed by rathbhupendra

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 begining 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 ");
    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 begining 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);
}
}
  
// This code is contributed
// by Arnab Kundu

Python

# 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 "%d" %(temp.data),
                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()
            
# This code is contributed by 
# Nikhil Kumar Singh(nickzuck_007)

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 begining 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); 
  
// This code is contributed 
// by Arnab Kundu 


Output:

Contents of Circular Linked List
11 2 56 12

You may like to see 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 implementation of insert delete operations for circular linked lists.

Please write comments if you find any bug in above code/algorithm, or find other ways to solve the same problem



This article is attributed to GeeksforGeeks.org

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