Reverse a LinkedList Algorithm

Reversing a Linked List

Problem Statement:  Reverse a Linked List. 

Given a Linked List of Nodes  : 

1->2->3->4->5->6 , reverse it so that the output is 6->5->4->3->2->1

My Approach: 

For this approach, we cannot the same LinkedListNode since it would point to the same memory location.

In the above example,
1 should point to null of the new List.
2 which is 1.next (original) should point to 1 of the new List.
3 which is 2.next (original) should point to 2 of the new List.
4 which is 3.next (original) should point to 3 of the new List.
5 which is 4.next (original) should point to 4 of the new List.
6 which is 5.next (original) should point to 5 of the new List.

This is where our logic ends.

1) LinkedListNode Class 

• This class has 2 Components of a Singly Linked List. 
• Value of the node
• Pointer to the Next Node.

     

    public class LinkedListNode
    {
        public int Val;
        public LinkedListNode next;

        public LinkedListNode(int x)
        {
            Val = x;
        }
    }

2) Actual Method to implement the logic.

     public static LinkedListNode ReverseAListIterative(LinkedListNode head)
    {

            LinkedListNode previous = null;
            LinkedListNode current = head;

            while (current != null)
            {
                LinkedListNode temp = current.next;
                current.next = previous;
                previous = current;
                current = temp;
            }

            return previous;
     }