Power of Two 判断一个数是不是2的幂

出处

http://www.programcreek.com/2014/07/leetcode-power-of-two-java/

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

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

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

}

public class Solution {
    public boolean isPowerOfTwo(int n) {
        if(n<=0)
            return false;
        while(n>1){
            int t=n>>1;
            int c=t<<1;
         
            if(n!=c)
                return false; //挺巧妙的
         
            n=n>>1;
        }
        return true;
    }
}