Add Two Numbers
Question
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.
example
**Input**: (2 -> 4 -> 3) + (5 -> 6 -> 4)
**Output**: 7 -> 0 -> 8
**Explanation**: 342 + 465 = 807.
Answer
这道题是两个数相加，只不过数是以链表的形式表示的。所以我们从低位向高位加，维护一个进位的变量即可。
# 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
"""
root = n = ListNode(0)
carry = 0
while l1 or l2 or carry:
v1 = v2 = 0
if l1:
v1 = l1.val
l1 = l1.next
if l2:
v2 = l2.val
l2 = l2.next
carry, val = divmod(v1 + v2 + carry, 10)
n.next = ListNode(val)
n = n.next
return root.next
