#!/usr/bin/env python3

# -*- encoding: utf-8 -*-

"""

@FileName : addTwoNumbers.py

@Author : 56

@Date : 2020-10-04

@Description: https://leetcode-cn.com/problems/add-two-numbers/

"""

# 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:

if l1 == None:

return l2

if l2 == None:

return l1

carry = 0

head = current = ListNode()

p1 = l1

p2 = l2

while p1 != None or p2 != None:

res = carry

node = p1 if p1 != None else p2

if p1 != None:

res += p1.val

p1 = p1.next

if p2 != None:

res += p2.val

p2 = p2.next

if res >= 10:

carry = 1

res -= 10

else:

carry = 0

node.val = res

current.next = node

current = node

if carry != 0:

current.next = ListNode(1)

return head.next