carry = 0
if val >= 10:
val -= 10
carry = 1
node = ListNode(val)
last.next = node
last = node
l2 = l2.next
if carry == 1:
node = ListNode(1)
last.next = node
head.traverse()
return head
if __name__ == '__main__':
l1 = ListNode.build_from_array([2, 4, 3])
l2 = ListNode.build_from_array([2, 4, 3])
ListNode.add_two_numbers(l1, l2)
l1 = ListNode.build_from_array([5])
l2 = ListNode.build_from_array([5])
ListNode.add_two_numbers(l1, l2)
l1 = ListNode.build_from_array([1])
l2 = ListNode.build_from_array([9, 8])
ListNode.add_two_numbers(l1, l2)
