微软面试题,倒置数组

namespace ConsoleApplication1
{
    /// <summary>
    /// 微软面试题，一整数数组｛1，2，3……｝
    /// 选择其中某个数，然后将次数放置数组末尾，
    /// 比此数大的数放在数组前端递增排列
    /// 在后面添加比次数小的数，递增排列
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
            //设定数组值为{1-20}
            int[] intArr = new int[20];
            for (int i = 0; i < intArr.Length; i++)
            {
                intArr[i] = i + 1;
            }

            //获取用户选择的数字
            Console.WriteLine("SelectElements(1-20):");
            int selectElement=Convert.ToInt32( Console.ReadLine());

            Func1(intArr,selectElement);

            Console.Read();
        }

        /// <summary>
        /// 输出重整序列的数组
        /// </summary>
        /// <param name="arr"></param>
        /// <param name="selectElement"></param>
        public static void Func1(int[] arr, int selectElement)
        {
            int index = -1;
            Swap(arr, 0, arr.Length - 1);
            for (int i = 0; i < arr.Length; i++)
            {
                if (arr[i] == selectElement)
                    index = i;
            }

            Swap(arr,0,index-1); 
            Swap(arr, index, arr.Length - 1);
            
            for (int i = 0; i < arr.Length; i++)
            {
                Console.WriteLine(arr[i].ToString());
            }
        }
        
        /// <summary>
        /// 倒置数组中某段的值
        /// </summary>
        /// <param name="arr"></param>
        /// <param name="beginIndex"></param>
        /// <param name="endIndex"></param>
        public static void Swap(int[] arr, int beginIndex, int endIndex)
        {
            int temp = -1;
            int swapTimes = -1;

            if ((endIndex - beginIndex + 1) % 2 == 0)
                swapTimes = (endIndex - beginIndex + 1) / 2;
            else
                swapTimes = (endIndex - beginIndex) / 2;

            for (int i = 0; i < swapTimes; i++)
            {
                temp = arr[beginIndex + i];
                arr[beginIndex + i] = arr[endIndex - i];
                arr[endIndex - i] = temp;
            }
        }
    }
}