231. Power of Two - jiejackyzhang/leetcode-note GitHub Wiki

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

##Approach 1

public class Solution {
    public boolean isPowerOfTwo(int n) {
        return n > 0 && Math.pow(2,30) % n == 0;
    }
}

##Approach 2 注意到power of 2有以下特征：8（1000），8-1（0111），8 & (8-1) == 0000。

public class Solution {
    public boolean isPowerOfTwo(int n) {
        if(n < 1) return false;
        return ((n-1) & n) == 0;
    }
}