标签：
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?
Credits:
Special thanks to @yukuairoy for adding this problem and creating all test cases.
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c++ code:
class Solution {
public:
bool isPowerOfFour(int num) {
return num>0 && (num&(num-1))==0 && (num-1)%3==0;
}
};标签：
原文地址：http://blog.csdn.net/itismelzp/article/details/51378040
