231. Power of Two

Given an integer, write a function to determine if it is a power of two.

就是看n是不是2的幂，n&(n-1)可以找出n中二进制下有多少1

public class Solution {
public boolean isPowerOfTwo(int n) {
if(n<=0)return false;
return ((n&(n-1))==0);//n&(n-1)用在判断二进制数中有多少个1存在非常好用
}
}