342. Power of Four
Description
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?
Solutions
Solution: Recursion
- Time complexity: O(1)
- Space complexity: O(1)
JavaScript
js
/**
* @param {number} n
* @return {boolean}
*/
const isPowerOfFour = function (n) {
if (n === 0) return false;
if (n === 1) return true;
if (n % 4 !== 0) return false;
return isPowerOfFour(n / 4);
};