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
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