319. Bulb Switcher
Brainteaser, Math, Review ·Problem Statement
link: LeetCode.cn LeetCode
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:
Input: n = 3
Output: 1
Input: n = 0
Output: 0
Input: n = 1
Output: 1
Solution Approach
Algorithm
Implement
class Solution:
def bulbSwitch(self, n: int) -> int:
# if factor is even : off, odd: on
return int(sqrt(n))