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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 ``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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