add LeetCode 206. 反转链表

Author: Chocolate1999

链表/LeetCode 206. 反转链表.md

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+![](https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jZG4uanNkZWxpdnIubmV0L2doL2Nob2NvbGF0ZTE5OTkvY2RuL2ltZy8yMDIwMDgyODE0NTUyMS5qcGc?x-oss-process=image/format,png)
+>仰望星空的人，不应该被嘲笑
+
+## 题目描述
+
+反转一个单链表。
+
+示例:
+
+```javascript
+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？
+
+来源：力扣（LeetCode）
+链接：https://leetcode-cn.com/problems/reverse-linked-list
+著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
+
+
+
+## 解题思路
+
+**非递归解法**
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+var reverseList = function(head) {
+    let pre = null;
+    let cur = head;
+    while(cur){
+        let tmp = cur.next;
+        cur.next = pre;
+        pre = cur;
+        cur = tmp;
+    }
+    return pre;
+};
+```
+
+**递归解法**
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+var reverseList = function (head) {
+    let reverse = (pre, cur) => {
+        if (!cur) return pre;
+        let tmp = cur.next;
+        cur.next = pre;
+        return reverse(cur, tmp);
+    }
+    return reverse(null, head);
+};
+```
+
+
+## 最后
+文章产出不易，还望各位小伙伴们支持一波！
+
+往期精选：
+
+<a href="https://github.com/Chocolate1999/Front-end-learning-to-organize-notes">小狮子前端の笔记仓库</a>
+
+<a href="https://github.com/Chocolate1999/leetcode-javascript">leetcode-javascript：LeetCode 力扣的 JavaScript 解题仓库，前端刷题路线（思维导图）</a>
+
+小伙伴们可以在Issues中提交自己的解题代码，🤝 欢迎Contributing，可打卡刷题，Give a ⭐️ if this project helped you!
+
+
+<a href="https://yangchaoyi.vip/">访问超逸の博客</a>，方便小伙伴阅读玩耍~
+
+![](https://img-blog.csdnimg.cn/2020090211491121.png#pic_center)
+
+```javascript
+学如逆水行舟，不进则退
+```
+
+