Add solution #89

Author: JoshCrozier

README.md

@@ -81,6 +81,7 @@
 83|[Remove Duplicates from Sorted List](./0083-remove-duplicates-from-sorted-list.js)|Easy|
 86|[Partition List](./0086-partition-list.js)|Medium|
 88|[Merge Sorted Array](./0088-merge-sorted-array.js)|Easy|
+89|[Gray Code](./0089-gray-code.js)|Medium|
 90|[Subsets II](./0090-subsets-ii.js)|Medium|
 93|[Restore IP Addresses](./0093-restore-ip-addresses.js)|Medium|
 94|[Binary Tree Inorder Traversal](./0094-binary-tree-inorder-traversal.js)|Easy|

solutions/0089-gray-code.js

@@ -0,0 +1,27 @@
+/**
+ * 89. Gray Code
+ * https://leetcode.com/problems/gray-code/
+ * Difficulty: Medium
+ *
+ * An n-bit gray code sequence is a sequence of 2n integers where:
+ * - Every integer is in the inclusive range [0, 2n - 1],
+ * - The first integer is 0,
+ * - An integer appears no more than once in the sequence,
+ * - The binary representation of every pair of adjacent integers differs
+ *   by exactly one bit, and
+ * - The binary representation of the first and last integers differs by
+ *   exactly one bit.
+ * Given an integer n, return any valid n-bit gray code sequence.
+ */
+
+/**
+ * @param {number} n
+ * @return {number[]}
+ */
+var grayCode = function(n) {
+  const result = [0];
+  for (let i = 0; i < n; i++) {
+    result.push(...result.map((v) => v | 1 << i).reverse());
+  }
+  return result;
+};