Reverse a singly linked list.
Example:
Input: 1->2->3->4->5->NULL Output: 5->4->3->2->1->NULL
Follow up:
A linked list can be reversed either iteratively or recursively. Could you implement both?
(Java) LeetCode 206. Reverse Linked List —— 反转链表
原文：https://www.cnblogs.com/tengdai/p/9279421.html