231. Power of Two

方法1：递归

public class Solution {    public boolean isPowerOfTwo(int n) {        if(n <= 0) return false;        if(n == 1) return true;        if(n>=2 && n%2== 0)            return isPowerOfTwo(n/2);        return false;    }}

方法2：位运算

public class Solution {    public boolean isPowerOfTwo(int n) {        if(n <= 0) return false;        return (n&(n-1)) == 0;    }}