（python）leetcode刷题笔记 02 Add Two Numbers

2. Add Two Numbers

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: ( ->  -> ) + ( ->  -> )
Output:  ->  ->
Explanation:  +  = .

 # Definition for singly-linked list.
 #class ListNode:
 #    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
         """
         if l1==None:
             return l2
         if l2==None:
             return l1
         carry=
         s=ListNode()
         ret=s
         while l1 or l2:#如果两个链表next均不为空
             sum=
             if l1:
                 sum+=l1.val
                 l1=l1.next
             if l2:
                 sum+=l2.val
                 l2=l2.next
             sum+=carry
             s.next=ListNode(sum%)
             s=s.next
             carry=(sum>=)
         if carry==:
             s.next=ListNode()
         del s
         return ret.next

ANSWER