Light Bulb Toggling - Amazon Top Interview Questions

Problem Statement :

You are given an integer n, and there's n switches in a room all in off position and n people who flip switches as follows:

Person 1 comes and flips all switches that are multiples of 1, so all of them.
Person 2 flips switches that are multiples of 2: 2, 4, 6, ...
Person i flips switches that are multiples of i.
Return number of switches that will be in on position at the end.


0 ≤ n < 2 ** 31

Example 1

n = 4


Initially the bulbs are [0, 0, 0, 0] (not set).

After player 1: [1, 1, 1, 1]
After player 2: [1, 0, 1, 0]
After player 3: [1, 0, 0, 0]
After player 4: [1, 0, 0, 1]
In the end there's 2 bulbs that are on and 2 that are off.

Solution :


                        Solution in C++ :

int solve(int n) {
    return sqrt(n);

                        Solution in Java :

import java.util.*;

class Solution {
    public int solve(int n) {
        int cnt = 0;
        for (long i = 1; i * i <= n; i++) {
        return cnt;

                        Solution in Python : 
class Solution:
    def solve(self, n):
        return floor(math.sqrt(n))

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