Dinesh on Java

In this article, we will discuss how to delete a given node from the singly linked list. Given a pointer to a node to be deleted but we don’t have a pointer to head node. In a singly linked list, each node in the list has the content and a pointer to the next node in the list. It does not store any pointer to the previous node. To store a single linked list, only the pointer to the first node in that list must be stored. The last node in a single linked list points to nothing.

In previous articles we have discussed some important algorithm related to the linked list like the following:

• Find the nth node from the end of a singly linked list
• Find the middle element in a linked list
• How to Reverse linked list in Java

In this article, we are going to discuss another important algorithm related to the Linked List. Let’s see as the following diagram:
As you can see that we will delete given node from singly linked list.

Delete given node from singly linked list

There are two approaches to delete given node from singly linked list at the following:

Approach 1: We have a pointer to head node

It is a very simple solution to traverse the linked list until you find the node you want to delete. But this solution requires the pointer to the head node which contradicts the problem statement.

Approach 2: We don’t have a pointer to head node

In this case, we can use a fast solution. We can copy the data from the next node to the node to be deleted and delete the next node as the following:

   // Find next node using next pointer
    Node temp  = node_ptr->next;
    // Copy data of next node to this node
    node_ptr->data  = temp->data;
    // Unlink next node
    node_ptr->ext  = temp->next;
    // Delete next node
    free(temp);

Let’s see the complete code:

/**
 * 
 */
package com.dineshonjava.algo;

import java.util.Optional;

/**
 * @author Dinesh.Rajput
 *
 */
public class LinkedListTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		Node listNode = createLinkedList(9);
		System.out.println("Before deleting"); 
		printList(listNode);
               deleteNode(listNode.next.next); 
               System.out.println("\nAfter Deleting"); 
               printList(listNode);
	}
	
	private static Node createLinkedList(int n) {
	    Node head = new Node("1");
	    Node current = head;
	 
	    for (int i = 2; i <= n; i++) { 
               Node newNode = new Node(String.valueOf(i)); 
               current.setNext(newNode); 
               current = newNode; 
            } 
          return head; 
        } 

       public static void deleteNode(Node Node_ptr) 
       { 
            Node temp = Node_ptr.next; 
            Node_ptr.data = temp.data; 
            Node_ptr.next = temp.next; 
            temp = null; 
      } 
      public static void printList(Node head) { 
          while (head != null) {
                System.out.print("->;"+head.getData());
		head = head.getNext();
	    }
	System.out.println();
	}
}

Run above program, you will get the following output:

Before deleting
->1->2->3->4->5->6->7->8->9

After Deleting
->1->2->4->5->6->7->8->9

As you can see the above output, we have deleted a node with data 3.

Hope, you have understood this solution for the above to delete given node from linked list. Please share other solutions if you have. :).

Happy learning with us!!!.