Last updated on February 28th, 2025 at 01:22 pm

Here, we see a Bulb Switcher II LeetCode Solution. This Leetcode problem is solved using different approaches in many programming languages, such as C++, Java, JavaScript, Python, etc.

List of all LeetCode Solution

Topics

Math

Companies

Microsoft

Level of Question

Medium

Bulb Switcher II LeetCode Solution

1. Problem Statement

There is a room with n bulbs labeled from 1 to n that all are turned on initially, and four buttons on the wall. Each of the four buttons has a different functionality where:

• Button 1: Flips the status of all the bulbs.
• Button 2: Flips the status of all the bulbs with even labels (i.e., 2, 4, …).
• Button 3: Flips the status of all the bulbs with odd labels (i.e., 1, 3, …).
• Button 4: Flips the status of all the bulbs with a label j = 3k + 1 where k = 0, 1, 2, … (i.e., 1, 4, 7, 10, …).

You must make exactly presses button presses in total. For each press, you may pick any of the four buttons to press.

Given the two integers n and presses, return the number of different possible statuses after performing all presses button presses.

Example 1:
Input: n = 1, presses = 1
Output: 2
Explanation: Status can be:
– [off] by pressing button 1
– [on] by pressing button 2

Example 2:
Input: n = 2, presses = 1
Output: 3
Explanation: Status can be:
– [off, off] by pressing button 1
– [on, off] by pressing button 2
– [off, on] by pressing button 3

Example 3:
Input: n = 3, presses = 1
Output: 4
Explanation: Status can be:
– [off, off, off] by pressing button 1
– [off, on, off] by pressing button 2
– [on, off, on] by pressing button 3
– [off, on, on] by pressing button 4

2. Coding Pattern Used in Solution

The provided coding pattern is a “Decision Tree Reduction” pattern. This pattern involves reducing a problem into a small set of possible outcomes based on the constraints and inputs. The code uses a series of conditional checks (if statements) to determine the number of unique light configurations based on the number of bulbs (n) and the number of presses (presses).

3. Code Implementation in Different Languages

3.1 Bulb Switcher II C++

class Solution {
public:
    int flipLights(int n, int presses) {
        if(presses == 0) return 1;
        if(n == 1) return 2;
        if(n == 2 && presses == 1) return 3;
        if(n == 2 || presses == 1) return 4;
        if(presses == 2) return 7;
        return 8;
    }
};

3.2 Bulb Switcher II Java

class Solution {
    public int flipLights(int n, int presses) {
        if(presses==0) return 1;
        if(n==1) return 2;
        if(n==2 && presses==1) return 3;
        if(n==2) return 4;
        if(presses==1) return 4;
        if(presses==2) return 7;
        if(presses>=3) return 8;
        return 8;
    }
}

3.3 Bulb Switcher II JavaScript

var flipLights = function(n, presses) {
    if (presses === 0) {
      return 1;
    } else if (n === 1) {
      return 2;
    } else if (n === 2) {
      return presses === 1 ? 3 : 4;
    } else {
      return presses === 1 ? 4 : presses === 2 ? 7 : 8;
    }
};

3.4 Bulb Switcher II Python

class Solution(object):
    def flipLights(self, n, presses):
        if(presses==0): return 1;
        if(n==1): return 2;
        if(n==2 and presses==1): return 3;
        if(n==2): return 4;
        if(presses==1): return 4;
        if(presses==2): return 7;
        if(presses>=3): return 8;
        return 8;

4. Time and Space Complexity

	Time Complexity	Space Complexity
C++	O(1)	O(1)
Java	O(1)	O(1)
JavaScript	O(1)	O(1)
Python	O(1)	O(1)

• The code is highly optimized for this specific problem and does not involve loops or recursion.
• The number of bulbs (n) and the number of presses (presses) are reduced to a small set of cases, making the solution efficient.
• The logic is based on mathematical reasoning about the symmetry and periodicity of the bulb states.