using System;

​

public class Node  {

    public int value = 0;

    public Node next;

    public Node(int value, Node next) {

        this.value = value;

        this.next = next;

    }

    public int Length() {

        Node next = this;

        int length = 0;

        while(next != null) {

            next = next.next;

            length++;

        }

        return length;

    }

}

public class Program

{

    public static void Main()

    {       

        Node intersect = new Node(2, new Node(3, null));

        Node node = findIntersectionNode(new Node(1, intersect), new Node(2, new Node(1, intersect)));

        if(node == null) {

            Console.WriteLine("No intersection!");  

        } else {

            Console.WriteLine(node.value); 

        }

    }

​

    public static Node findIntersectionNode(Node list1, Node list2)

    {       

        // SINCE all we are focusing on is the tail end we simply need to determine WHEN we reach the tail

        // Calculate the lengths of the list 

        int length1 = list1.Length();

        int length2 = list2.Length();

        Node dominantList;

        Node servantList;

        int difference = 0;

        int listLength = 0;

        if(length1 < length2) {

            dominantList = list2;

            servantList = list1;

            difference = length2 - length1;

            listLength = length1;

        } else {

            dominantList = list1;

            servantList = list2;

            difference = length1 - length2;

            listLength = length2;

        }

        // Trim down the dominant list until we have lists the same length

        while(difference > 0) {

            dominantList = dominantList.next;

            difference--;

        }

        Node sharedNode = null;

        // Housekeeping done, start on the list 

        for(int x = 0; x < (listLength - 1); x++) {

            if(dominantList == servantList) {

                return dominantList;

            }

            dominantList = dominantList.next;

            servantList = servantList.next;

        }

        return sharedNode;

    }

}