To make it faster, use `while l1 or l2`

instead of `while l1 and l2`

+ `while l1`

+ `while l2`

. `h`

is dummy head.

```
def addTwoNumbers(self, l1, l2):
h = ListNode(0)
p, carry = h, 0
while l1 or l2:
Sum = carry
if l1:
Sum, l1 = Sum + l1.val, l1.next
if l2:
Sum, l2 = Sum + l2.val, l2.next
p.next, carry = ListNode(Sum % 10), Sum / 10
p = p.next
p.next = ListNode(carry) if carry else None
return h.next
```