The diffcult part of this problem is to handle carefully about the linked list.
# Definition for singly-linked list.
class ListNode:
def __init__(self, x):
self.val = x
self.next = None
class Solution:
def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
head = ListNode(None)
current = head
exceed = 0
while l1 or l2 or exceed:
if l1 is None:
a = 0
else:
a = l1.val
l1 = l1.next
if l2 is None:
b = 0
else:
b = l2.val
l2 = l2.next
current.next = ListNode((a + b + exceed) % 10)
current = current.next
exceed = (a + b + exceed) // 10
return head.next