Leetcode # 326. Power of Three

Problem

https://leetcode.com/problems/power-of-three

Solution

⚠️ 注意 if 順序

if n == 1: return True
if n < 1 or n % 3 != 0: return False

if n < 1 or n % 3 != 0: return False
if n == 1: return True

因為 1 % 3 == 1 != 0 會導致if n == 1執行不到

Code

Time Complexity: O(log(n, 3)) = O(log(n))
Space Complexity: O(log(n, 3)) = O(log(n))
(The input and output generally do not count towards the space complexity.)

class Solution:
  def isPowerOfThree(self, n: int) -> bool:
    if n == 1: return True
    if n < 1 or n % 3 != 0: return False
    return self.isPowerOfThree(n // 3)

Last Updated on 2025/08/13 by A1go