二分法查找

#region 二分法查找
        static void InitBinData()
        {
            const int n = 20;
            int[] a = new int[n];
            Random r = new Random();
            for (int i = 0; i < n; ++i)
            {
                a[i] = r.Next(1, 21);
                Console.Write("  " + a[i]);
            }
            Console.WriteLine();
            BubbleSort(a);
            for (int i = 0; i < n; ++i)
            {
                Console.Write("  " + a[i]);
            }
            Console.WriteLine();
            Console.WriteLine("请输入查找的值");
            int value = Convert.ToInt32(Console.ReadLine());
            bool isOK = Binsrch(a, n, value);
            
            Console.WriteLine("是否找到" + isOK);
        }
        static bool Binsrch( int[] a, int n, int value )
        {
            
            int start = 0;
            int end = n - 1;
            int mid = 0;

            while ( start <= end )
            {
                mid = ((start + end) >> 1);
                if ( value < a[mid] )
                {
                    end = mid - 1;
                }
                else if ( value > a[mid] )
                {
                    start = mid + 1;
                } 
                else
                {
                    return true;
                }
            }
            return false;
        }
        #endregion