0401-binary-watch.js

/**
 * 401. Binary Watch
 * https://leetcode.com/problems/binary-watch/
 * Difficulty: Easy
 *
 * A binary watch has 4 LEDs on the top to represent the hours (0-11), and 6 LEDs on the bottom
 * to represent the minutes (0-59). Each LED represents a zero or one, with the least significant
 * bit on the right.
 * - For example, the below binary watch reads "4:51".
 * Given an integer turnedOn which represents the number of LEDs that are currently on (ignoring
 * the PM), return all possible times the watch could represent. You may return the answer in
 * any order.
 * The hour must not contain a leading zero.
 * - For example, "01:00" is not valid. It should be "1:00".
 * The minute must consist of two digits and may contain a leading zero.
 * - For example, "10:2" is not valid. It should be "10:02".
 */

/**
 * @param {number} turnedOn
 * @return {string[]}
 */
var readBinaryWatch = function(turnedOn) {
  const result = [];

  for (let h = 0; h < 12; h++) {
    for (let m = 0; m < 60; m++) {
      if (h.toString(2).split('1').length - 1 + m.toString(2).split('1').length - 1 === turnedOn) {
        result.push(`${h}:${m < 10 ? '0' + m : m}`);
      }
    }
  }

  return result;
};