leetcode 链表 两数相加

 两数相加

给定两个非空链表来表示两个非负整数。位数按照逆序方式存储，它们的每个节点只存储单个数字。将两数相加返回一个新的链表。

你可以假设除了数字 0 之外，这两个数字都不会以零开头。

示例：

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

 # Definition for singly-linked list.
 class ListNode:
     def __init__(self, x):
         self.val = x
         self.next = None

 class Solution:
     def addTwoNumbers(self, l1, l2):
         """
         :type l1: ListNode
         :type l2: ListNode
         :rtype: ListNode
         """
         head = ListNode(0)
         cur = head
         m = 0
         while True:
             if l1 is not None:
                 a = l1.val
             else:
                 a = 0
             if l2 is not None:
                 b = l2.val
             else:
                 b = 0
             if l1 is None and l2 is None and m == 0:
                 return head.next
             else:
                 add = a + b + m
                 cur.next = ListNode(add % 10)
                 m = (a+b+m) // 10
                 cur = cur.next
             if l1 is not None:
                 l1 = l1.next
             if l2 is not None:
                 l2 = l2.next