[342] Power of Four

【题目描述】

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】

跟326思路一样

【代码】

class Solution {
public:
    bool isPowerOfFour(int num) {
        double ans=log(num)/log(4);
        return (ans-int(ans))==0?true:false;
    }
};