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`

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