Reverse Linked List

Author: w2xi

README.md

@@ -13,6 +13,7 @@
 |66|[加一](https://leetcode-cn.com/problems/plus-one/)|[JavaScript](./algorithms/plus-one.js)|Easy|
 |136|[只出现一次的数字](https://leetcode-cn.com/problems/single-number/)|[JavaScript](./algorithms/single-number.js)|Easy|
 |189|[轮转数组](https://leetcode-cn.com/problems/rotate-array/)|[JavaScript](./algorithms/rotate-array.js)|Medium|
+|206|[反转链表](https://leetcode-cn.com/problems/reverse-linked-list/)|[JavaScript](./algorithms/reverse-linked-list.js)|Easy|
 |344|[反转字符串](https://leetcode-cn.com/problems/reverse-string/)|[JavaScript](./algorithms/reverse-string.js)|Easy|
 |349|[两个数组的交集](https://leetcode-cn.com/problems/intersection-of-two-arrays/)|[JavaScript](./algorithms/intersection-of-two-arrays.js)|Easy|
 |350|[两个数组的交集 II](https://leetcode-cn.com/problems/intersection-of-two-arrays-ii/)|[JavaScript](./algorithms/intersection-of-two-arrays-ii.js)|Easy|

algorithms/reverse-linked-list.js

@@ -0,0 +1,51 @@
+// 常规解法
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+var reverseList = function (head) {
+  let hNode;
+  
+  while (head) {
+    hNode = new ListNode(head.val, hNode);
+
+    head = head.next;
+  }
+
+  return hNode || head;
+};
+
+// 迭代法
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+ var reverseList = function(head) {
+  let prev = null;
+  let curr = head
+
+  while (curr) {
+      let next = curr.next
+      curr.next = prev
+      prev = curr
+      curr = next
+  }
+
+  return prev
+};