[leetcode]Add Two Numbers @ Python

原题地址：https://oj.leetcode.com/problems/add-two-numbers/

题意：

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

解题思路：链表的操作。

代码：

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    # @return a ListNode
    def addTwoNumbers(self, l1, l2):
        if l1 == None: return l2
        if l2 == None: return l1
        flag = 0
        dummy = ListNode(0); p = dummy
        while l1 and l2:
            p.next = ListNode((l1.val+l2.val+flag) % 10)
            flag = (l1.val+l2.val+flag) / 10
            l1 = l1.next; l2 = l2.next; p = p.next
        if l2:
            while l2:
                p.next = ListNode((l2.val+flag) % 10)
                flag = (l2.val+flag) / 10
                l2 = l2.next; p = p.next
        if l1:
            while l1:
                p.next = ListNode((l1.val+flag) % 10)
                flag = (l1.val+flag) / 10
                l1 = l1.next; p = p.next
        if flag == 1: p.next = ListNode(1)
        return dummy.next