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 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++

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// 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;
}

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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
        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

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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
        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

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Output:

List after deletion : 57 11 61

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



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Strategy Path planning and Destination matters in success No need to worry about in between temporary failures

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