leetcode-go/leetcode/medium/319.bulb-switcher.go

func bulbSwitchSlow(n int) (res int) { // Brute search, TLE
	bulbs := make([]bool, n)
	for i := 1; i <= n; i++ {
		for j := i-1; j < n; j += i {
			bulbs[j] = !bulbs[j]
		}
	}
	for i := 0; i < n; i++ {
		if bulbs[i] {
			res++
		}
	}
	return
}

func bulbSwitch(n int) int { // Math
	return int(math.Sqrt(float64(n)))
}