231. Power of Two

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

Solution1:

检查1的个数，略麻烦。

public class Solution {
    public boolean isPowerOfTwo(int n) {
        if(n==0||n==Integer.MIN_VALUE)
        {
            return false;
        }
        int count=0;
        for(int i=0;i<=32;i++)
        {
            if(count>1)
            {
                return false;
            }
            if(((n>>>i)&1)==1)
            {
                count++;
            }
        }
        return true;
    }
}

Solution2:

清零法，跟之前有一道题目很像

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