leetcode--2.两数相加

 1 # Definition for singly-linked list.
 2 # class ListNode(object):
 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         #定义change递归函数，遍历链表，依次乘以10并且相加，重构成一个整数
15         def change(node):
16             return node.val + 10*change(node.next) if node else 0
17         
18         #把两个整数相加
19         num = change(l1) + change(l2)
20         
21         #将该整数转换成字符串
22         s = str(num)[::-1]
23         
24         #新建一个值为0的节点并指定索引
25         l4 = l3 = ListNode(0)
26         
27         #遍历转换后的字符串形式的和将其值依次赋予链表
28         for i in s:
29             l3.next = ListNode(i)
30             l3 = l3.next
31         return l4.next
32