Description：
You are given two non-empty linked lists representing two non-negative integers. The digits
are stored in reverse order and each of their nodes contain a single digit. Add the two
numbers and return it as a linked list. You may assume the two numbers do not contain any leading zero, except the number 0 itself.
给定两个非空链表（里面的数字可以是0），数字是逆序（非大小关系，即自然数相加减要从各位开始算）排放，最后输出正确顺序的结果
Example：
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.
Solutions：
1 # Definition for singly-linked list. 2 # class ListNode(object): 3 # def __init__(self, x): 4 # self.val = x 5 # self.next = None 6 7 class Solution: 8 # @return a ListNode 9 def addTwoNumbers(self, l1, l2): 10 carry = 0 11 root = n = ListNode(0) 12 while l1 or l2 or carry: 13 v1 = v2 = 0 14 if l1: 15 v1 = l1.val 16 l1 = l1.next # 依次往后 17 if l2: 18 v2 = l2.val 19 l2 = l2.next 20 carry, val = divmod(v1+v2+carry, 10) 21 n.next = ListNode(val) 22 n = n.next 23 return root.next
Python 内置函数 divmod() 函数
python divmod() 函数把除数和余数运算结果结合起来，返回一个包含商和余数的元组(a // b, a % b)。
>>>divmod(7, 2)
(3, 1)