Add solution #61

Author: JoshCrozier

README.md

@@ -66,6 +66,7 @@
 58|[Length of Last Word](./0058-length-of-last-word.js)|Easy|
 59|[Spiral Matrix II](./0059-spiral-matrix-ii.js)|Medium|
 60|[Permutation Sequence](./0060-permutation-sequence.js)|Hard|
+61|[Rotate List](./0061-rotate-list.js)|Medium|
 62|[Unique Paths](./0062-unique-paths.js)|Medium|
 64|[Minimum Path Sum](./0064-minimum-path-sum.js)|Medium|
 65|[Valid Number](./0065-valid-number.js)|Hard|

solutions/0061-rotate-list.js

@@ -0,0 +1,37 @@
+/**
+ * 61. Rotate List
+ * https://leetcode.com/problems/rotate-list/
+ * Difficulty: Medium
+ *
+ * Given the head of a linked list, rotate the list to the right by k places.
+ */
+
+/**
+ * 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 (!head || !head.next || !k) return head;
+  let tailCopy = head;
+  let tail = head;
+  let count = 1;
+  while (tail.next) {
+    tail = tail.next;
+    count++;
+  }
+  tail.next = head;
+  for (let i = 1; i < count - k % count; i++) {
+    tailCopy = tailCopy.next;
+  }
+  const result = tailCopy.next;
+  tailCopy.next = null;
+  return result;
+};