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