Delete all odd nodes of a Circular Linked List

Prerequiste: 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++

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// 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;
}

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Java

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// 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);
    }
}

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Python

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# 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) 

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C#

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// 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);
    }
}

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Output:

List after deletion : 56 12 2

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