You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode ln1, head;
int flag = 0;
head = ln1 = new ListNode(0);
while (l1 != null || l2 != null