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: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 Explanation: 342 + 465 = 807.
1 # Definition for singly-linked list. 2 #class ListNode: 3 # def __init__(self, x): 4 # self.val = x 5 # self.next = None 6 7 class Solution(object): 8 def addTwoNumbers(self, l1, l2): 9 """ 10 :type l1: ListNode 11 :type l2: ListNode 12 :rtype: ListNode 13 """ 14 if l1==None: 15 return l2 16 if l2==None: 17 return l1 18 carry=0 19 s=ListNode(0) 20 ret=s 21 while l1 or l2:#如果两个链表next均不为空 22 sum=0 23 if l1: 24 sum+=l1.val 25 l1=l1.next 26 if l2: 27 sum+=l2.val 28 l2=l2.next 29 sum+=carry 30 s.next=ListNode(sum%10) 31 s=s.next 32 carry=(sum>=10) 33 if carry==1: 34 s.next=ListNode(1) 35 del s 36 return ret.next