Method addLists

java/Chapter 2/Question2_5/QuestionB.java:26–41

(LinkedListNode l1, LinkedListNode l2)

	}
	
	private static LinkedListNode addLists(LinkedListNode l1, LinkedListNode l2) {
		int len1 = length(l1);
		int len2 = length(l2);
		if (len1 < len2) {
			l1 = padList(l1, len2 - len1);
		} else {
			l2 = padList(l2, len1 - len2);
		}
		PartialSum sum = addListsHelper(l1, l2);
		if (sum.carry == 0) {
			return sum.sum;
		} else {
			LinkedListNode result = insertBefore(sum.sum, sum.carry);
			return result;
		}
	}	
	
	private static LinkedListNode padList(LinkedListNode l, int padding) {
		LinkedListNode head = l;