Data Structures

Circular Linked List - 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 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 C program to demonstrate traversal. Following is complete C program to demonstrate traversal of circular linked list.

#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\n ");
    printList(head);

    return 0;
}

# 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)

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


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