Delete /remove all nodes of a single linked list in java (example/non-recursive)

• Given a single linked list, we will delete all nodes of single linked list
  • i.e. We want to delete the single linked list.
• We have shown the single linked list in Fig 1.
  • We will traverse the single linked list.
  • We will delete the nodes of single linked list during traversal.
  • At end of iteration the whole linked list will be deleted.

• We will simulate the deletion of head node from linked list
  • Similar procedure can be followed for rest of the nodes of linked list.
• We have shown the deletion of node in Fig 2.
  • One thing, we need to take care that before we delete any node, we have to ensure that we store its next reference (next node in linked list) , otherwise we will lose the single linked list.

Algorithm – delete/remove all nodes of a single linked list in java

• Create the variable Node backup = null
  • backup variable will be used to store the reference of next node of linked list
• Start the traversing the single linked list using head reference
• Store the reference of next node i.e. Node 5 [Step 1 shown in Fig 2]
  • backup = head.next
  • backup will start pointing to Node 5
• Set the head reference to null
  • head = null (GC will take care of deleting it)
• Restore the head to next node
  • head = backup
  • So that we can delete rest of nodes in linked list
• Keep on iterating through the single linked list
• Once we finished the iteration, Complete linked list will be deleted.

Time complexity of algorithm is O(n).

Program – Delete/remove all nodes of single linked list in java.

1.) DeleteLinkedList Class:

• delete method method delete all nodes in a single linked list (one by one)
• insert method is used to insert elements or node to a single linked list
  • insert function is used to create linked list
• print method is used to print the single linked list

package org.learn.Question;

import org.learn.List.Node;

public class DeleteLinkedList {

	public static Node delete(Node head) {
		Node backup = null;
		while (head != null) {
			backup = head.next;
			head = null;
			head = backup;
		}
		return head;
	}

	public static void insert(Node head, int data) {
		while (head.next != null)
			head = head.next;
		head.next = new Node(data);
	}

	public static void print(Node head) {
		while (head != null) {
			System.out.printf("%d ", head.data);
			head = head.next;
		}
		System.out.println("");
	}
}

2.) App Class:

• We are creating the single linked list using DeleteLinkedList.insert method.
• We are printing the linked list using DeleteLinkedList.print method.
• We are calling DeleteLinkedList.delete method, to delete all nodes in a single linked list

package org.learn.Client;

import org.learn.List.Node;
import org.learn.Question.DeleteLinkedList;

public class App {
	public static void main(String[] args) {
		int[] data = { 9, 5, 2, 8, 10, 9, 1 };
		Node head = new Node(data[0]);
		for (int count = 1; count < data.length; count++)
			DeleteLinkedList.insert(head, data[count]);

		System.out.printf("Linked list is : ");
		DeleteLinkedList.print(head);

		head = DeleteLinkedList.delete(head);
		if (head == null) {
			System.out.println("Deleted all nodes in linked list");
		} else {
			System.out.println("Could not able to delete all nodes from linked list");
		}
	}
}

3.) Node Class:

• Node class representing the node(s) of single linked list

package org.learn.List;

public class Node {
	public int data;
	public Node next;

	public Node(int num) {
		this.data = num;
		this.next = null;
	}
}

Output – delete/remove all nodes of  a single linked list in java

Linked list is : 10 20 10 20 50 20 50
Deleted all nodes in linked list

Download code – delete/ remove all nodes of single linked list in java