CareerCup

using System;
					
public class Program
{
	public static void Main()
	{
		Node n1 = new Node(9);
		Node n2 = new Node(9);
		Node n3 = new Node(9);
		
		n1.next = n2;
		n2.next = n3;
		
		
		Node n4 = new Node(1);
		Node n5 = new Node(2);
		Node n6 = new Node(3);
		
		n4.next = n5;
		n5.next = n6;
		
		Node nr = MultiPly (n1 , n4);
		Node cursor = nr;
		while(cursor != null)
			{
				Console.Write(cursor.data);
				cursor = cursor.next;
			}
	}
	public static Node MultiPly (Node head1 , Node head2)
	{
		Node number1 = Reverse(head1);
		Node number2 = Reverse(head2);
		
		int ret;
		int carryout = 0;
		Node result = new Node(0);
		Node reultHead = result;
		Node resultCur = result;
		while(number2 != null)
		{
			Node marker = number1;
			result = resultCur;
			carryout = 0;
			while(marker != null)
			{
				
			  //Console.WriteLine(carryout);
			   ret = (marker.data * number2.data);
			   result.data = ret + result.data + carryout;
				if (result.data > 9)
				{
					carryout = result.data/10;
					result.data = result.data%10;
					
				}	
				
				if ( result.next == null)
				{
					Node resultnext = new Node(0);
					result.next = resultnext;
				}
				//Console.WriteLine(marker.data + " * " + number2.data + "=" + result.data ) ;
				result = result.next;
				marker = marker.next;
			}
			if (carryout > 0)
			{
				result.data = carryout;
			}
			number2 = number2.next;
			resultCur = resultCur.next;
		}
		
		return Reverse(reultHead);
		
	}
	public static Node Reverse (Node head)
	{
		Node cur = head;
		Node prev = null;
		Node next = null;
		
			while (cur != null)
		{
			next = cur.next;
			cur.next = prev;
			prev = cur;
			cur = next;
		}
		return prev;
	}
	public class Node{
		
		
		public Node prev;
		public Node next;
		public int data ;
		public Node (int d)
		{
			this.data = d;
		}
	
	}
}

Is there a condition for not having extra space or recursion ?

Number 1 : 25, represented as [2] -> [5] -> null
Number 2: 5, represented as [5] -> null

Bogus solution could be to convert the linkedlist into strings, then parse it back into integers. I'm sure this isn't what they're looking for.

public int multiplyLLNumbers(LinkedList one, LinkedList 2)
{
	Node node = one.Head();
	String temp = "";
	while(onenode.next() != null)
	{
		temp += node.data.toString();
	}
	
	String temp2 = "";
	node = two.Head();
	while(two.next() != null)
	{
		temp2 += two.data.toString();
	}
	
	return (Integer.parseInt(temp1) * Integer.parseInt(temp2));
}