23w1: add leetcode 61 solution

Author: swiftwind0405

README.md

@@ -383,7 +383,7 @@
 |64|[Minimum Path Sum](https://leetcode.com/problems/minimum-path-sum/)| |Medium|
 |63|[Unique Paths II](https://leetcode.com/problems/unique-paths-ii/)| |Medium|
 |62|[Unique Paths](https://leetcode.com/problems/unique-paths/)| |Medium|
-|61|[Rotate List](https://leetcode.com/problems/rotate-list/)| |Medium|
+|61|[Rotate List](https://leetcode.com/problems/rotate-list/)| [js](./algorithms/rotateList/Solution.js) |Medium|
 |60|[Permutation Sequence](https://leetcode.com/problems/permutation-sequence/)| |Medium|
 |59|[Spiral Matrix II](https://leetcode.com/problems/spiral-matrix-ii/)| |Medium|
 |58|[Length of Last Word](https://leetcode.com/problems/length-of-last-word/)| |Easy|

algorithms/rotateList/Solution.js

@@ -0,0 +1,41 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @param {number} k
+ * @return {ListNode}
+ */
+var rotateRight = function (head, k) {
+    if (k === 0 || !head) {
+        return head
+    }
+    let current = head
+    let index = 0
+    let length = 0
+    while (current.next) {
+        current = current.next
+        length++
+    }
+    // 没计算尾节点因此需要再+1
+    length++
+    // k对长度取余，k有可能超过本身链表的长度
+    let _k = k % length
+    // 把首尾节点接上
+    current.next = head
+    current = head
+    // 继续遍历链表，当前节点加上旋转长度如果已经超出了长度，就代表是尾节点了
+    while (current.next && index + _k < length - 1) {
+        current = current.next
+        index++
+    }
+
+    // 当前节点是尾节点，需要断开
+    const result = current.next
+    current.next = null
+    return result
+};