Java Program To Delete Alternate Nodes Of A Linked List

// Java program to delete alternate 
// nodes of a linked list
class LinkedList
{
    // Head of list
    Node head;  
 
    // Linked list Node
    class Node
    {
        int data;
        Node next;
        Node(int d) 
        {
            data = d; 
            next = null; 
        }
    }

    void deleteAlt()
    {
       if (head == null) 
          return;

       Node prev = head;
       Node now = head.next;

       while (prev != null && 
              now != null) 
       {           
           // Change next link of previous node 
           prev.next = now.next;

           // Free node 
           now = null;

           // Update prev and now 
           prev = prev.next;
           if (prev != null) 
              now = prev.next;
       }
    }                 

                    
    // Utility functions 
    // Inserts a new Node at front 
    // of the list. 
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node new_node = new Node(new_data);
 
        // 3. Make next of new Node as head 
        new_node.next = head;
 
        // 4. Move the head to point to 
        // new Node 
        head = new_node;
    }

    // Function to print linked list 
    void printList()
    {
        Node temp = head;
        while(temp != null)
        {
           System.out.print(temp.data + " ");
           temp = temp.next;
        }  
        System.out.println();
    }

     // Driver code
    public static void main(String args[])
    {
        LinkedList llist = new LinkedList();
        
        /* Constructed Linked List is 
           1->2->3->4->5->null */
        llist.push(5);
        llist.push(4);
        llist.push(3);
        llist.push(2);
        llist.push(1);
        
        System.out.println(
               "Linked List before calling deleteAlt() ");
        llist.printList();
        
        llist.deleteAlt();
        
        System.out.println(
               "Linked List after calling deleteAlt() ");
        llist.printList();
    }
} 
// This code is contributed by Rajat Mishra 

/* Deletes alternate nodes of 
   a list starting with head */
static Node deleteAlt(Node head) 
{ 
    if (head == null) 
        return; 

    Node node = head.next; 

    if (node == null) 
        return; 

    // Change the next link of head 
    head.next = node.next; 


    /* Recursively call for the new 
       next of head */
    head.next = deleteAlt(head.next); 
} 
// This code is contributed by Arnab Kundu