class Solution { public: bool isPowerOfFour(int num) { if(num<=0) return false; else { int test = 0x55555555; int MaxPowerOfFour = 0x01<<30; return MaxPowerOfFour % num ? false:((test&num)==num?true:false); } } };
原文：http://www.cnblogs.com/shihaochangeworld/p/5547430.html