原題鏈接：https://leetcode.com/problems/power-of-four/description/
這道題目我沒想出實現來，看得討論區別人的答案：

/**
 * Created by clearbug on 2018/2/26.
 */
public class Solution {

    public static void main(String[] args) {
        Solution s = new Solution();
        System.out.println(s.isPowerOfFour(5));
        System.out.println
 
(s.isPowerOfFour(8));
        System.out.println(s.isPowerOfFour(16));
    }

    public boolean isPowerOfFour(int num) {
        return num > 0 && (num & (num - 1)) == 0 && (num & 0x55555555) != 0;
    }

}

342. Power of Four