二分法排序

class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("请输入一个正序排列的整数数组，用空格分割，最后按回车键结束输入：");
            string[] ValueStr = Console.ReadLine().Split(' ');
            Console.WriteLine("请输入要查询的数值：");
            int value = int.Parse(Console.ReadLine().Trim());

            int[] Items = new int[ValueStr.Length];
            for (int i = 0; i < ValueStr.Length; i++)
            {
                Items[i] = int.Parse(ValueStr[i].Trim());
            }
            Console.WriteLine("你要查询数值的位置为：" + binarySearch(Items, value).ToString());
            Console.ReadLine();
        }
        private static int binarySearch(int[] Items, int value)
        {
            if(Items.Length==1)
            {
                return 0;
            }
            int StartIndex = 0;
            int EndIndex = Items.Length - 1;
            int MiddleIndex = (EndIndex + StartIndex) / 2 ;
            while (Items[MiddleIndex] != value)
            {
                if (Items[MiddleIndex] > value)
                {
                    EndIndex = MiddleIndex - 1;
                    MiddleIndex = (EndIndex + StartIndex) / 2;
                }
                else
                {
                    StartIndex = MiddleIndex + 1;
                    MiddleIndex = (EndIndex + StartIndex) / 2;
                }
            }
            return MiddleIndex;
        }
    }

来源：https://www.cnblogs.com/shuwang/archive/2010/04/22/1718108.html