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.

Constraints

0 ≤ n < 2 ** 31


Example 1

Input
n = 4

Output
2

Explanation
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 :



title-img 




                        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++) {
            cnt++;
        }
        return cnt;
    }
}
                    


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


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