https://leetcode.com/problems/power-of-four/description/
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?
题目翻译
题目解析
判断一个数是不是4的幂。
参考答案
class Solution {
public:
bool isPowerOfFour(int num) {
//2 8 32 false 2=0010 8=1000 32=0010,0000
//4 16 64 true 4=0100 16=0001,0000 64=0100,0000
//5=0101
if(num <= 0) return false;
return (((num&(num-1))==0) && (num&0x55555555));
}
};
