leetcode231. Power of Two

231. Power of Two

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

解法一

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

    }
}

解法二

public class Solution {
    public boolean isPowerOfTwo(int n) {
        return n>0 && Integer.bitCount(n) == 1;
    }
}

解法三

public class Solution {
    public boolean isPowerOfTwo(int n) {
        return n>0 && (n==1 || (n%2==0 && isPowerOfTwo(n/2)));
    }
}