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Delete all odd nodes of a Circular Linked List
  • Difficulty Level : Basic
  • Last Updated : 17 May, 2021

Prerequisite: Delete all the even nodes of a Circular Linked List
Given a circular singly linked list containing N nodes, the task is to delete all the odd nodes from the list.
 

Examples:
 

Input: 572->112->21->5->1->6 
Output: 572 -> 112 -> 6 
Explanation: All the odd valued nodes have been deleted
Input: 9->11->32->6->13->20 
Output: 32 -> 6 -> 20 

 



 

Approach: 
The idea is to traverse the nodes of the circular singly linked list one by one and get the pointer of the nodes having odd data. Delete those nodes by following the approach used in this post.
Below is the implementation of the above idea:
 

C++




// C++ program to delete all odd
// node from a Circular singly linked list
 
#include <bits/stdc++.h>
using namespace std;
 
// 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
        // For the first node
        ptr1->next = ptr1;
 
    *head_ref = ptr1;
}
 
// Delete the node if it is odd
void deleteNode(Node* head_ref, Node* del)
{
    struct Node* temp = head_ref;
    // If node to be deleted is head node
 
    if (head_ref == del)
        head_ref = del->next;
 
    // Traverse list till not found
    // delete node
    while (temp->next != del) {
        temp = temp->next;
    }
 
    // Copy address of node
    temp->next = del->next;
 
    // Finally, free the memory occupied by del
    free(del);
    return;
}
 
// Function to delete all odd nodes
// from the singly circular linked list
void deleteoddNodes(Node* head)
{
    struct Node* ptr = head;
 
    struct Node* next;
 
    // Traverse list till the end
    // if the node is odd then delete it
    do {
        // if node is odd
        if ((ptr->data % 2) == 1)
 
            deleteNode(head, ptr);
        // point to next node
        next = ptr->next;
        ptr = next;
    } while (ptr != head);
}
 
// Function to print nodes
void printList(struct Node* head)
{
    struct Node* temp = head;
    if (head != NULL) {
        do {
            printf("%d ", temp->data);
            temp = temp->next;
        } while (temp != head);
    }
}
 
// Driver code
int main()
{
    // Initialize lists as empty
    struct Node* head = NULL;
 
    // Created linked list will be 56->61->57->11->12->2
    push(&head, 2);
    push(&head, 12);
    push(&head, 11);
    push(&head, 57);
    push(&head, 61);
    push(&head, 56);
 
    cout << "\nList after deletion : ";
    deleteoddNodes(head);
    printList(head);
 
    return 0;
}

Java




// Java program to delete all prime
// node from a Circular singly linked list
class GFG {
 
    // Structure for a 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;
            return head_ref;
        }
        else
// For the first node
            ptr1.next = ptr1;
 
        head_ref = ptr1;
        return head_ref;
    }
 
    // Delete the node if it is odd
    static Node deleteNode(Node head_ref, Node del)
    {
        Node temp = head_ref;
        // If node to be deleted is head node
 
        if (head_ref == del)
            head_ref = del.next;
 
        // Traverse list till not found
        // delete node
        while (temp.next != del) {
            temp = temp.next;
        }
 
        // Copy address of node
        temp.next = del.next;
 
        return head_ref;
    }
 
    // Function to delete all odd nodes
    // from the singly circular linked list
    static Node deleteoddNodes(Node head)
    {
        Node ptr = head;
 
        Node next;
 
        // Traverse list till the end
        // if the node is odd then delete it
        do {
            // If node is odd
            if (ptr.data % 2 == 1)
                deleteNode(head, ptr);
 
            // point to next node
            next = ptr.next;
            ptr = next;
        } while (ptr != head);
        return head;
    }
 
    // Function to print nodes
    static void printList(Node head)
    {
        Node temp = head;
        if (head != null) {
            do {
                System.out.printf("%d ", 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 56->61->57->11->12->2
        head = push(head, 2);
        head = push(head, 12);
        head = push(head, 11);
        head = push(head, 57);
        head = push(head, 61);
        head = push(head, 56);
 
        System.out.println("\nList after deletion : ");
        head = deleteoddNodes(head);
        printList(head);
    }
}

Python




# Python3 program to delete all odd
# node from a Circular singly linked list
import math
   
# Structure for a node
class Node: 
    def __init__(self, data): 
        self.data = data 
        self.next = None
   
# Function to insert a node at the beginning
# of a Circular linked list
def push(head_ref, data):
    ptr1 = Node(data)
    temp = head_ref
    ptr1.data = data
    ptr1.next = head_ref
   
    # If linked list is not None then
    # set the next of last node
    if (head_ref != None):
        while (temp.next != head_ref):
            temp = temp.next
        temp.next = ptr1
           
    else:
        ptr1.next = ptr1 # For the first node
   
    head_ref = ptr1
    return head_ref
   
# Delete the node if it is odd
def deleteNode(head_ref, delete):
    temp = head_ref
       
    # If node to be deleted is head node
    if (head_ref == delete):
        head_ref = delete.next
   
    # Traverse list till not found
    # delete node
    while (temp.next != delete):
        temp = temp.next
       
    # Copy address of node
    temp.next = delete.next
       
   
# Function to delete all odd nodes
# from the singly circular linked list
def deleteoddNodes(head):
    ptr = head
    next = None
   
    # Traverse list till the end
    # if the node is odd then delete it
    # if node is odd
    next = ptr.next
    ptr = next
    while (ptr != head):
        if (ptr.data % 2 == 1):
            deleteNode(head, ptr)
   
        # po to next node
        next = ptr.next
        ptr = next
    return head
   
# Function to pr nodes
def prList(head):
    temp = head
    if (head != None):
        print(temp.data, end = " ")
        temp = temp.next
        while (temp != head):
            print(temp.data, end = " ")
            temp = temp.next
           
# Driver code
if __name__=='__main__'
       
    # Initialize lists as empty
    head = None
   
    # Created linked list will be 56->61->57->11->12->2 
    head = push(head, 2
    head = push(head, 12)
    head = push(head, 11
    head = push(head, 57
    head = push(head, 61
    head = push(head, 56)
   
    print("List after deletion : ", end = "")
    head = deleteoddNodes(head)
    prList(head)

C#




// C# program to delete all prime
// node from a Circular singly linked list
using System;
 
class GFG {
 
    // Structure for a node
    public 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;
            return head_ref;
        }
        else
            // For the first node
            ptr1.next = ptr1;
 
        head_ref = ptr1;
        return head_ref;
    }
 
    // Delete the node if it is odd
    static Node deleteNode(Node head_ref, Node del)
    {
        Node temp = head_ref;
 
        // If node to be deleted is head node
        if (head_ref == del)
            head_ref = del.next;
 
        // Traverse list till not found
        // delete node
        while (temp.next != del) {
            temp = temp.next;
        }
 
        // copy address of node
        temp.next = del.next;
 
        return head_ref;
    }
 
    // Function to delete all odd nodes
    // from the singly circular linked list
    static Node deleteoddNodes(Node head)
    {
        Node ptr = head;
 
        Node next;
 
        // Traverse list till the end
        // if the node is odd then delete it
        do {
            // If node is odd
            if (ptr.data % 2 == 1)
                deleteNode(head, ptr);
 
            // Point to next node
            next = ptr.next;
            ptr = next;
        } while (ptr != head);
        return head;
    }
 
    // Function to print nodes
    static void printList(Node head)
    {
        Node temp = head;
        if (head != null) {
            do {
                Console.Write("{0} ", 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 56->61->57->11->12->2
        head = push(head, 2);
        head = push(head, 12);
        head = push(head, 11);
        head = push(head, 57);
        head = push(head, 61);
        head = push(head, 56);
 
        Console.WriteLine("\nList after deletion : ");
        head = deleteoddNodes(head);
        printList(head);
    }
}
Output: 
List after deletion : 56 12 2

 

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