206.反转链表.js

/*
 * @lc app=leetcode.cn id=206 lang=javascript
 *
 * [206] 反转链表
 *
 * https://leetcode-cn.com/problems/reverse-linked-list/description/
 *
 * algorithms
 * Easy (70.60%)
 * Likes:    1354
 * Dislikes: 0
 * Total Accepted:    375.6K
 * Total Submissions: 529.2K
 * Testcase Example:  '[1,2,3,4,5]'
 *
 * 反转一个单链表。
 *
 * 示例:
 *
 * 输入: 1->2->3->4->5->NULL
 * 输出: 5->4->3->2->1->NULL
 *
 * 进阶:
 * 你可以迭代或递归地反转链表。你能否用两种方法解决这道题？
 *
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function (head) {
    var prev = null;
    var node = head;
    var next = null;
    while (node !== null) {
      next = node.next;
      node.next = prev;
  
      prev = node;
      node = next;
    }
    return prev;
  };
// @lc code=end