leetcode---Power of Four

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?

思路：

换成二进制后，最高位为1，,剩余都为0，且0的个数为偶数

class Solution {
public:
bool isPowerOfFour(int num) {
int c = 0;
while(num)
{
if(num & 1)
break;
c++;
num >>= 1;
}
if(c%2==0 && num==1)
return true;
else
return false;
}
};