Package g0301_0400.s0319_bulb_switcher

Class Solution

java.lang.Object
g0301_0400.s0319_bulb_switcher.Solution
public class Solution extends java.lang.Object
319 - Bulb Switcher.

Medium

There are n bulbs that are initially off. You first turn on all the bulbs, then you turn off every second bulb.

On the third round, you toggle every third bulb (turning on if it’s off or turning off if it’s on). For the ith round, you toggle every i bulb. For the nth round, you only toggle the last bulb.

Return the number of bulbs that are on after n rounds.

Example 1:

Input: n = 3

Output: 1

Explanation: At first, the three bulbs are [off, off, off]. After the first round, the three bulbs are [on, on, on]. After the second round, the three bulbs are [on, off, on]. After the third round, the three bulbs are [on, off, off]. So you should return 1 because there is only one bulb is on.

Example 2:

Input: n = 0

Output: 0

Example 3:

Input: n = 1

Output: 1

Constraints:

  • 0 <= n <= 109

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    bulbSwitch(int n)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • bulbSwitch

      public int bulbSwitch(int n)