BulbSwitcher_II.js

// Source : https://leetcode.com/problems/bulb-switcher-ii
// Author : Dean Shi
// Date   : 2017-09-05

/***************************************************************************************
 *
 * There is a room with n lights which are turned on initially and 4 buttons on the
 * wall. After performing exactly m unknown operations towards buttons, you need to
 * return how many different kinds of status of the n lights could be.
 *
 * Suppose n lights are labeled as number [1, 2, 3 ..., n], function of these 4 buttons
 * are given below:
 *
 * Flip all the lights.
 * Flip lights with even numbers.
 * Flip lights with odd numbers.
 * Flip lights with (3k + 1) numbers, k = 0, 1, 2, ...
 *
 * Example 1:
 *
 * Input: n = 1, m = 1.
 * Output: 2
 * Explanation: Status can be: [on], [off]
 *
 * Example 2:
 *
 * Input: n = 2, m = 1.
 * Output: 3
 * Explanation: Status can be: [on, off], [off, on], [off, off]
 *
 * Example 3:
 *
 * Input: n = 3, m = 1.
 * Output: 4
 * Explanation: Status can be: [off, on, off], [on, off, on], [off, off, off], [off,
 * on, on].
 *
 * Note:
 * n and m both fit in range [0, 1000].
 *
 *
 ***************************************************************************************/

/**
 * @param {number} n
 * @param {number} m
 * @return {number}
 */
var flipLights = function(n, m) {
    if (m === 0 || n === 0) return 1
    if (n === 1) return 2
    if (n === 2) return m === 1 ? 3 : 4
    if (m === 1) return 4
    return m === 2 ? 7 : 8
};