# Problem 231: Power of Two

> <https://leetcode.com/problems/power-of-two/>

## 思路

## ![](https://1241747088-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lpv9LvBSlFaukf_ALqh%2F-Lpv9NPw3Ji1X5Vk8CES%2F-Lpv9uv0oGQZZkAm6jEm%2FcheckPow2.jpg?generation=1569729532339226\&alt=media)

```java
public class Solution {
    public boolean isPowerOfTwo(int n) {
        if (n <= 0) {
            return false;
        }

        return ((n - 1) & n) == 0;
    }
}
```

## 易错点

1. 这道题里认为 0 不算平方，所以开头要把它排除
2. 做 & 运算加括号！否则会先判断 n == 0

   ```java
   return ((n - 1) & n) == 0;
   ```