using System;

public class Program

{

    public static void Main()

    {

        var list = new LinkedList<int>(new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 });

        Console.WriteLine($"normal: {list}");

        list.Reverse();

        Console.WriteLine($"reversed: {list}");     

    }

}

​

public class Node<T>

    {

        public T Value;

        public Node<T> Next;

    }

​

    public class LinkedList<T>

    {

        private Node<T> startNode;

​

        public LinkedList(T[] startingValues)

        {

            Node<T> previousNode = null;

            for (int i = 0; i < startingValues.Length; i++)

            {

                var node = new Node<T>

                {

                    Value = startingValues[i]

                };

​

                if (previousNode != null)

                {

                    previousNode.Next = node;

                }

​

                previousNode = node;

                if(startNode == null){

                    startNode = node;

                }

            }

        }

​

        public void Reverse()

        {

            Node<T> previousNode = null;

            Node<T> currentNode = startNode;

            Node<T> nextNode = null;

            while (currentNode != null)

            {

                nextNode = currentNode.Next;

                // Always set next of current node so the last node (atm first) will point to null, indicating the end of the list

                currentNode.Next = previousNode;

​

                previousNode = currentNode;

                currentNode = nextNode;

            }

            startNode = previousNode;

        }

​

        public override string ToString()

        {

            string result = string.Empty;

​

            var currentNode = startNode;

​

            while (currentNode != null)

            {

                result += $"{currentNode.Value},";

​

                currentNode = currentNode.Next;

            }

​

            // Do Substring to remove last trailing comma

            return result.Substring(0, result.Length - 1);

        }

    }