Power of Four

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

An integer n is a power of four, if there exists an integer x such that n == 4x.

Example 1:

Input: n = 16
Output: true

Example 2:

Input: n = 5
Output: false

Example 3:

Input: n = 1
Output: true

Constraints:

• -231 <= n <= 231 - 1

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

class Solution:
    def isPowerOfFour(self, n: int) -> bool:
        bi = "{:b}".format(n)
        return n > 0 and bi.count("1") == 1 and bi[::-1].index("1") % 2 == 0