LeetCode342. Power of Four

一、题目

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?

二、题解

class Solution {
public:
    bool isPowerOfFour(int n) {
        return n > 0 && (n == (n & -n)) && (n & 0xaaaaaaaa) == 0;
    }
};