C# 实验课

一、实验目的熟悉string、StringBuilder、math、random类用法；熟悉常用集合使用熟悉泛型技术二、实验内容2、定义一个静态成员方法，该方法实现字符串反转。自行设计程序验证上述方法正确性。   public static string Reverse(string str)   {      //方法主体中使用StringBuilder   }3、假定已经获取题库中的试题号，并存放在数组arrayKT中。例如， int [] arrayKT={10,13,18,19,20,22,30,31...}。定义一个静态成员方法，该方法实现从上述数组中随机抽出给定数量(n，1<=n<=arrayKT.Length)的考题,并组成一个考题字符串。比如，随机从arrayKT中抽取5题组成考题字符串：“10,18,20,22,30”。要求，组成考题字符串中考题不重复，且一定在数组中存在。自行设计程序验证上述方法正确性。   public static string getKTH(int n,param int [] arrayKT)   {      //提示：主体中使用random类   }4、数列a的各项表达式为：a1= ，a2= ，a3= ，…。编写控制台应用程序，计算数列的极限值(n=1000)。

using System;using System.Collections.Generic;using System.Linq;using System.Text;//include StringBuilderusing System.Collections;using System.Threading;namespace ConsoleApplication1{    class Program    {        static void Main(string[] args)        {            Console.WriteLine("Experience_1");            Console.WriteLine(Exam.getFileNames("c:\\program files\\Maths\\all.dat"));            Console.WriteLine("Experience_2");            string str = "abcdcd";            Console.WriteLine(Exam.Reverse(str));            Console.WriteLine("Experience_3");            int[] arrayKT = { 10, 13, 18, 19, 20, 22, 30, 31 };            for (int i = 0; i < 3; i++)            {                str = Exam.getKTH(3, arrayKT);                Console.WriteLine(str);                            }            Console.WriteLine("Experience_4");            Console.WriteLine(Exam.cal());            Console.Read();        }    }    class Exam    {        /* 获取文件名         * string strFilePaht="文件路径";          * Path.GetFileNameWithoutExtension(strFilePath);         * 这个就是获取文件名的还有的就是用Substring截取          * strFilePaht.Substring(path.LastIndexOf("\\") + 1, path.Length - 1 - path.LastIndexOf("\\"));          * strFilePaht.Substring(path.LastIndexOf("."), path.Length - path.LastIndexOf("."));         * 提问者评价或者用openFileDialog1.SafeFileName         */        public static string getFileNames(string file)//1        {            return file.Substring(file.LastIndexOf("\\") + 1);        }               public static string Reverse(string str)//2        {            ////solution 1使用ctrl+E && ctrl+U删除注释            //stringbuilder sbuilder = new stringbuilder();            //sbuilder.append(str);            //int length = str.length;            //char temp;            //for (int i = 0; i < length / 2; i++)            //{            //    temp = sbuilder[i];            //    sbuilder[i] = sbuilder[length - i - 1];            //    sbuilder[length - i - 1] = temp;            //}            //str = sbuilder.tostring();            //return str;            //solution 2            int length = str.Length;            StringBuilder sbuilder = new StringBuilder();            Stack stack = new Stack();            for (int i = 0; i < length; i++)            {                stack.Push(str[i]);            }            for (int i = 0; i < length; i++)            {                sbuilder.Append((char)stack.Pop());            }            str = sbuilder.ToString();            return str;        }               public static string getKTH(int n, params int[] arrayKT)//3        {            //question : why the num is same; the function of foreach            Random rand = new Random();            string str;            int tmp, length = arrayKT.Length;            bool [] used = new bool[length];            for (int i = 0; i < length; i++)            {                used[i] = true;            }            tmp = rand.Next(length);            str = arrayKT[tmp].ToString();            used[tmp] = false;            for (int i = 0; i < n - 1; i++)            {                while (true)                {                    tmp = rand.Next(length);                    if (used[tmp])                    {                        str += "," + arrayKT[tmp].ToString();                        used[tmp] = false;                        break;                    }                }            }            //using Random()            return str;        }                public static double cal()//4        {            double[] a = new double[1001];            a[1] = Math.Sqrt(2);            for (int i = 2; i <= 1000; i++)            {                a[i] = Math.Sqrt(a[i - 1] + 2d);                Console.WriteLine(Math.Sqrt(a[i] + 2d));            }            Console.WriteLine(Math.Sqrt(a[1] + 2d));            return a[1000];        }         }}