0089-gray-code.js

/**
 * 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;
};