[leetcode] 231. Power of Two

题目

Given an integer n, return true if it is a power of two. Otherwise, return false.

An integer n is a power of two, if there exists an integer x such that n == 2x.

Example 1:

Input: n = 1
Output: true
Explanation: 20 = 1

Example 2:

Input: n = 16
Output: true
Explanation: 24 = 16

Example 3:

Input: n = 3
Output: false

Constraints:

• -2^31 <= n <= 2^31 - 1

Follow up: Could you solve it without loops/recursion?

思路

列出所有2的幂，然后判断n是否在此中。

代码

python版本：

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        nums = [pow(2, i) for i in range(32)]
        return True if n in nums else False