判断当前数值，是否为2的n次方

///   <summary>
         ///  主要思路
         ///  应用了位运算
         ///   </summary>
         public   static   void  FinB()
        {
             int  n  =  Convert.ToInt32(Console.ReadLine());
             if (n == 0 )
            {
                Console.WriteLine( " N " );
                Console.ReadKey();
                 return ;
            }
             if  (n  !=   1 )
            {
                 // n和n-1进行与运算，当n为4(二进制100),4-1为3(二进制11)值等于0，值为0时说明当前数值为2的N次方
                Console.WriteLine((n  &  (n  -   1 ))  ==   0   ?  (Convert.ToString(n,  2 ).Length  -   1   +   " Y " ) :  " N " );
            }
             else
            {
                Console.WriteLine( " Y " );
            }

            Console.ReadKey();
        }