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Delete all the even nodes of a Circular Linked List

  • Difficulty Level : Medium
  • Last Updated : 21 May, 2021

Given a circular singly linked list containing N nodes, the task is to delete all the even nodes from the list.
 

Examples: 
 

Input : 57->11->2->56->12->61 
Output : List after deletion : 57 -> 11 -> 61 

Input : 9->11->32->6->13->20
Output : List after deletion : 9 -> 11 -> 13 

 

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



C++




// CPP program to delete all even
// 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
        ptr1->next = ptr1; // For the first node
 
    *head_ref = ptr1;
}
 
// Delete the node if it is even
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 even nodes
// from the singly circular  linked list
void deleteEvenNodes(Node* head)
{
    struct Node* ptr = head;
 
    struct Node* next;
 
    // traverse list till the end
    // if the node is even then delete it
    do {
        // if node is even
        if (ptr->data % 2 == 0)
            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 57->11->2->56->12->61
    push(&head, 61);
    push(&head, 12);
    push(&head, 56);
    push(&head, 2);
    push(&head, 11);
    push(&head, 57);
 
    cout << "\nList after deletion : ";
    deleteEvenNodes(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
        ptr1.next = ptr1; // For the first node
 
    head_ref = ptr1;
return head_ref;
}
 
// Delete the node if it is even
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 even nodes
// from the singly circular linked list
static Node deleteEvenNodes(Node head)
{
    Node ptr = head;
 
    Node next;
 
    // traverse list till the end
    // if the node is even then delete it
    do
    {
        // if node is even
        if (ptr.data % 2 == 0)
            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 57.11.2.56.12.61
    head=push(head, 61);
    head=push(head, 12);
    head=push(head, 56);
    head=push(head, 2);
    head=push(head, 11);
    head=push(head, 57);
 
    System.out.println( "\nList after deletion : ");
    head=deleteEvenNodes(head);
    printList(head);
}
}
 
// This code is contributed by Arnab Kundu

Python3




# Python3 program to delete all even
# 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 even
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
     
    # Finally, free the memory occupied by delete
 
# Function to delete all even nodes
# from the singly circular linked list
def deleteEvenNodes(head):
    ptr = head
    next = None
 
    # traverse list till the end
    # if the node is even then delete it
    # if node is even
    next = ptr.next
    ptr = next
    while (ptr != head):
        if (ptr.data % 2 == 0):
            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 57.11.2.56.12.61
    head = push(head, 61)
    head = push(head, 12)
    head = push(head, 56)
    head = push(head, 2)
    head = push(head, 11)
    head = push(head, 57)
 
    print("List after deletion : ", end = "")
    head = deleteEvenNodes(head)
    prList(head)
     
# This code is contributed by Srathore

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
        ptr1.next = ptr1; // For the first node
 
    head_ref = ptr1;
return head_ref;
}
 
// Delete the node if it is even
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 even nodes
// from the singly circular linked list
static Node deleteEvenNodes(Node head)
{
    Node ptr = head;
 
    Node next;
 
    // traverse list till the end
    // if the node is even then delete it
    do
    {
        // if node is even
        if (ptr.data % 2 == 0)
            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 57.11.2.56.12.61
    head=push(head, 61);
    head=push(head, 12);
    head=push(head, 56);
    head=push(head, 2);
    head=push(head, 11);
    head=push(head, 57);
 
    Console.WriteLine( "\nList after deletion : ");
    head=deleteEvenNodes(head);
    printList(head);
}
}
 
// This code has been contributed by 29AjayKumar

Javascript




<script>
// javascript program to delete all prime
// node from a Circular singly linked list     // Structure for a node
class Node {
    constructor() {
        this.data = 0;
        this.next = null;
    }
}
 
    // Function to insert a node at the beginning
    // of a Circular linked list
    function push(head_ref , data) {
var ptr1 = new Node();
var 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
            ptr1.next = ptr1; // For the first node
 
        head_ref = ptr1;
        return head_ref;
    }
 
    // Delete the node if it is even
    function deleteNode(head_ref,  del) {
var 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 even nodes
    // from the singly circular linked list
    function deleteEvenNodes(head) {
var ptr = head;
 
var next;
 
        // traverse list till the end
        // if the node is even then delete it
        do {
            // if node is even
            if (ptr.data % 2 == 0)
                deleteNode(head, ptr);
 
            // povar to next node
            next = ptr.next;
            ptr = next;
        } while (ptr != head);
        return head;
    }
 
    // Function to prvar nodes
    function printList(head) {
var temp = head;
        if (head != null) {
            do {
                document.write( temp.data+" ");
                temp = temp.next;
            } while (temp != head);
        }
    }
 
    // Driver code
     
        // Initialize lists as empty
var head = null;
 
        // Created linked list will be 57.11.2.56.12.61
        head = push(head, 61);
        head = push(head, 12);
        head = push(head, 56);
        head = push(head, 2);
        head = push(head, 11);
        head = push(head, 57);
 
        document.write("\nList after deletion : ");
        head = deleteEvenNodes(head);
        printList(head);
 
// This code contributed by umadevi9616
</script>
Output: 
List after deletion : 57 11 61

 

Time Complexity: O(N), where N is the total number of nodes.
 

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