leetcode 2.两数相加

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