Add Two Number
https://oj.leetcode.com/problems/add-two-numbers/
Add Two Number
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
题目：两个链表代表的两个数字相加，逆向表示。
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 # @param {ListNode} l1 9 # @param {ListNode} l2 10 # @return {ListNode} 11 def addTwoNumbers(self, l1, l2): 12 if l1==None:return l2 #在最开始的时候，其中有任意的值为空，即个位数都为空，相加直接返回另一个数 13 if l2==None:return l1 14 dummy=ListNode(0) 15 p=dummy 16 flag=0 #对进位的计数 17 while l1 and l2: 18 p.next=ListNode((l1.val+l2.val+flag)%10) 19 flag=(l1.val+l2.val+flag)/10 20 l1=l1.next;l2=l2.next;p=p.next 21 if l1: #当前面的while l1和l2每一位都不为空结束时，若l1较长还有高数位的数，l2已为空时 22 while l1: 23 p.next=ListNode((l1.val+flag)%10) 24 flag=(l1.val+flag)/10 25 l1=l1.next;p=p.next 26 if l2: #l2比l1位数更多时 27 while l2: 28 p.next=ListNode((l2.val+flag)%10) 29 flag=(l2.val+flag)/10 30 l2=l2.next;p=p.next 31 if flag==1: #最终还有一个进位时 32 p.next=ListNode(1) 33 return dummy.next
