public class AddTwoNumber {

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

ListNode dummy = new ListNode(0), cur = dummy;

for (int carry = 0; l1 != null || l2 != null || carry > 0; ) {

int n1 = l1 != null ? l1.val : 0;

l1 = l1 != null ? l1.next : null;

int n2 = l2 != null ? l2.val : 0;

l2 = l2 != null ? l2.next : null;

int sum = n1 + n2 + carry;

ListNode node = new ListNode(sum % 10);

carry = sum / 10;

cur.next = node;

cur = node;

}

return dummy.next;

}

}