输入人数，输入分数，求平均分，升序降序排列

 ArrayList al = new ArrayList();
            Console.Write("请输入班级人数：");
            int n = int.Parse(Console.ReadLine());
            double sum = 0;
            for (int i = 0; i < n; i++)
            {
                Console.Write("请输入第" + (i + 1) + "个人的分数：");
                al.Add(double.Parse(Console.ReadLine()));
                sum += double.Parse(al[i].ToString());
            }
            Console.WriteLine("班级平均分是："+sum / n);
            al.Sort();
            Console.WriteLine("成绩从低到高排列是：");
            foreach(double fenshu in al)
            {
                Console.WriteLine(fenshu);
            }
            al.Reverse();
            Console.WriteLine("成绩从高到低排列是：");
            foreach(double fenshu in al)
            {
                Console.WriteLine(fenshu);
            }
            Console.ReadLine();