给定两个非空链表来表示两个非负整数。位数按照逆序方式存储，它们的每个节点只存储单个数字。将两数相加返回一个新的链表。
你可以假设除了数字 0 之外，这两个数字都不会以零开头。
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: 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 len1 = 0 19 len2 = 0 20 head = l1 21 while head!=None: 22 len1 +=1 23 head = head.next 24 25 head = l2 26 while head!= None: 27 len2 +=1 28 head = head.next 29 30 if len1 > len2: 31 shorter = len2 32 longer = len1 33 else: 34 shorter = len1 35 longer = len2 36 37 carry = 0 38 sum = None 39 while shorter != None: 40 value = longer.val + shorter.val + carry 41 carry = value / 10 42 value -= carry * 10 43 if sum = 0: 44 sum = ListNode(value) 45 result = sum 46 else: 47 sum.next = ListNode(value) 48 sum = sum.next 49 50 longer = longer.next 51 shorter = shorter.next 52 53 while longer != None: 54 value = longer.val + carry 55 carry = value / 10 56 value -= carry * 10 57 58 sum.next = ListNode(value) 59 sum = sum.next 60 61 longer = longer.next 62 63 if carry != 0: 64 sum.next = ListNode(carry) 65 66 return result 67 68 69 70