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?
一刷
题解：保证二进制的形式只有一个1，并且1出现在奇数位。
class Solution {
public boolean isPowerOfFour(int num) {
return num>0 &&(num&(num-1)) == 0 &&(num & 0x55555555) !=0;
//so that the single 1 bit always appears at the odd position
//0x55555555 is to get rid of those power of 2 but not power of 4
}
}
