Problem
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
/**
* @param {number} n
* @return {boolean}
*/
var isPowerOfFour = function(n) {
var num = 0b1010101010101010101010101010101;
return n > 0 && (n & (n - 1)) === 0 && (n & num) === n;
};
Explain:
nope.
Complexity:
- Time complexity : O(1).
- Space complexity : O(1).