0319-bulb-switcher.js

/**
 * 319. Bulb Switcher
 * https://leetcode.com/problems/bulb-switcher/
 * Difficulty: Medium
 *
 * There are n bulbs that are initially off. You first turn on all the bulbs, then you turn
 * off every second bulb.
 *
 * On the third round, you toggle every third bulb (turning on if it's off or turning off if
 * it's on). For the ith round, you toggle every i bulb. For the nth round, you only toggle
 * the last bulb.
 *
 * Return the number of bulbs that are on after n rounds.
 */

/**
 * @param {number} n
 * @return {number}
 */
var bulbSwitch = function(n) {
  return Math.floor(n ** 0.5);
};