leetcode--Power of Two

题目：Power of Two

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

One：以n为参数 n/2为变化率进行循环Iterable

public class Solution {
    public boolean isPowerOfTwo(int n) {
       if(n==1)return true;
       while(n!=0){
           if(n==1)return true;
           if(n%2!=0)break;
             n/=2;
       }
       
        return false;
    }
}

Two：进一步简化

public class Solution {
    public boolean isPowerOfTwo(int n) {
       if(n==1)return true;
       while(n%2==0){
             n/=2;
       }
        return n==1;
    }
}

Three:递归的方法Recursive

public class Solution {
    public boolean isPowerOfTwo(int n) {
       if(n==1)return true;
       if(n<1||n%2 !=0)return false;
        return isPowerOfTwo(n/2);
    }
}

Four：Recursive进一步简化

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