342. Power of Four(easy)

Easy

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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?

 

C++:

/*
 * @Autor: SourDumplings
 * @Date: 2019-09-11 08:10:46
 * @Link: https://github.com/SourDumplings/
 * @Email: changzheng300@foxmail.com
 * @Description: https://leetcode.com/problems/power-of-four/
 */

class Solution
{
public:
    bool isPowerOfFour(int num)
    {
        double d = log(num) / log(4);
        return fabs(d - (int)d) < 1e-5;
    }
};

 Java:

/*
 * @Autor: SourDumplings
 * @Date: 2019-09-11 08:15:35
 * @Link: https://github.com/SourDumplings/
 * @Email: changzheng300@foxmail.com
 * @Description: https://leetcode.com/problems/power-of-four/
 */

class Solution
{
    public boolean isPowerOfFour(int num)
    {
        return (Math.log(num) / Math.log(4)) % 1 == 0;
    }
}