* Definition for singly-linked list.
* public class ListNode {
* ListNode(int x) { val = x; }
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode p1 = l1, p2 = l2;
ListNode dummy = new ListNode(0);
ListNode curNode = dummy;
while (p1 != null || p2 != null) {
curNode.next = new ListNode(sum % 10);
curNode.next = new ListNode(sum);