# Java: One line solution

• `````` public int bulbSwitch(int n) {
return (int)Math.sqrt(n);
}``````

• package solution;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class BulbSwitchSolution {

``````public static void main(String[] args) {
// First Take input from user for n
Scanner user_input = new Scanner(System.in);
System.out.println("Enter an integer");
int n = user_input.nextInt();
System.out.println("You entered integer " + n);

// Initialize to 0 or OFF

List<Integer> list = new ArrayList<Integer>();
for (int i = 1; i <= n + 1; i++) {
list.add(0);

}

System.out.println("size is " + list.size());

for (int j = 1; j <= n; j++) {
System.out.print(list.get(j));
}
System.out.println();

for (int i = 1; i <= n; i++) {

// For 1st Iteration toggle to 1
if (i == 1) {
for (int j = 1; j <= n; j++) {
list.set(j, 1);
}
}

for (int j = 1; j <= n; j++) {
System.out.print(list.get(j));
}

System.out.println();

switchBulb(i + 1, n, list);

for (int j = 1; j <= n; j++) {
System.out.print(list.get(j));
}
System.out.println();
}
int count = 0;
for (int i = 1; i <= n; i++) {
if (list.get(i) == 1) {
count++;
}

}
System.out.println("count of ON " + count);
user_input.close();
}

private static void switchBulb(int i, int n, List<Integer> list) {
System.out.println("n is " + n + "i is: " + i);
for (int j = i; j <= n; j++) {
if (j % i == 0) {
if (list.get(j) == 1) {
list.set(j, 0);
} else {
list.set(j, 1);
}

}
}

}
``````

}

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