You are given two non-empty linked lists representing two non-negative integers. 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.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Example:
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.
2 个逆序的链表,要求从低位开始相加,得出结果也逆序输出,返回值是逆序结果链表的头结点。
需要注意的是各种进位问题。
极端情况,例如
Input: (9 -> 9 -> 9 -> 9 -> 9) + (1 -> )
Output: 0 -> 0 -> 0 -> 0 -> 0 -> 1
为了处理方法统一,可以先建立一个虚拟头结点,这个虚拟头结点的 Next 指向真正的 head,这样 head 不需要单独处理,直接 while 循环即可。另外判断循环终止的条件不用是 p.Next != nil,这样最后一位还需要额外计算,循环终止条件应该是 p != nil。