# 342. Power of Four

**<font color=red>难度: Easy</font>**

## 刷题内容

> 原题连接

* https://leetcode.com/problems/power-of-four/description/

> 内容描述

```
Given an integer (signed 32 bits), write a function to check whether it is a power of 4.

Example 1:

Input: 16
Output: true
Example 2:

Input: 5
Output: false
Follow up: Could you solve it without loops/recursion?
```

## 解题方案

> 思路 1
******- 时间复杂度: O(1)******- 空间复杂度: O(1)******

recursive

```java
class Solution {
    public boolean isPowerOfFour(int num) {
        if (num <= 0)
        	return false;
        if (num == 1)
        	return true;
        if (num % 4 == 0)
        	return isPowerOfFour(num/4);
        return false;
    }
}
```
