給定兩個非空鏈表來表示兩個非負整數。位數按照逆序方式存儲，它們的每個節點只存儲單個數字。將兩數相加返回一個新的鏈表。

你可以假設除了數字 0 之外，這兩個數字都不會以零開頭。

示例：

輸入：(2 -> 4 -> 3) + (5 -> 6 -> 4)
輸出：7 -> 0 -> 8
原因：342 + 465 = 807

 1 # Definition for singly-linked list.
 2 class ListNode:
 3     def __init__(self, x):
 4         self.val = x
 
 5         self.next = None
 6 
 7 
 8 class Solution:
 9     def addTwoNumbers(self, l1, l2):
10         """
11         :type l1: ListNode
12         :type l2: ListNode
13         :rtype: ListNode
14         """
15         head = ListNode(0)
16         cur = head
17         m = 0
18         while True:
 
19             if l1 is not None:
20                 a = l1.val
21             else:
22                 a = 0
23             if l2 is not None:
24                 b = l2.val
25             else:
26                 b = 0
27             if l1 is None and l2 is None and m == 0:
28                 return head.next
 
29             else:
30                 add = a + b + m
31                 cur.next = ListNode(add % 10)
32                 m = (a+b+m) // 10
33                 cur = cur.next
34             if l1 is not None:
35                 l1 = l1.next
36             if l2 is not None:
37                 l2 = l2.next

leetcode 鏈表 兩數相加