```
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def addTwoNumbers(self, l1, l2):
"""
:type l1: ListNode
:type l2: ListNode
:rtype: ListNode
"""
head = hasHead = False
c = 0
while l1 != None or l2 != None:
if hasHead == False:
tail = head = ListNode(c)
tmp = ListNode(0)
else:
tmp = ListNode(c)
tail.next = tmp
tail = tmp
if l1 != None:
if hasHead:
tmp.val += l1.val
else:
head.val += l1.val
l1 = l1.next
if l2 != None:
if hasHead:
tmp.val += l2.val
else:
head.val += l2.val
l2 = l2.next
c = tail.val / 10
tail.val %= 10
hasHead = True
if c != 0:
tail.next = ListNode(c)
return head
```

No algorithm inside. Not smart either but somehow effective.