题目

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

Example:
Given num = 16, return true. Given num = 5, return false.

Follow up: Could you solve it without loops/recursion?

解题思路

循环整除

代码

func isPowerOfFour(num int) bool {
    if 0 >= num {
        return false
    }
    
    if 1 == num {
        return true 
    }
    for ;num > 4 && num % 4 == 0; {
        num = num / 4
    }
    
    if num % 4 == 0 {
        return true
    }
    
    return false
}