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:
-231 <= n <= 231 - 1