Console.WriteLine("输入一个三位数的正整数，按数字的相反顺序输出");
            int num = Convert.ToInt32(Console.ReadLine());
            int bai =( num-(num % 100) )/ 100;
            int ge = (num % 100) % 10;
            int shi = ((num % 100)- ge) / 10;
            Console.WriteLine("你输入的整数是：{0}，结果为：{1}{2}{3}", num, ge, shi, bai);

            Console.WriteLine("输入电报数据");
            int number = Convert.ToInt32(Console.ReadLine());
            int wan = (number - (number % 10000)) / 10000;
            int qian = ((number - (wan * 10000)) - (number - (wan * 10000)) % 1000) / 1000;
            int bai = ((number - (wan * 10000)- (qian * 1000)) - ((number - (wan * 10000) - (qian * 1000)) % 100)) / 100;//57640-50000-7000=640-40
            int ge = number % 10;
            int shi = ((((number - (wan * 10000) - (qian * 1000)) % 100))-ge) / 10;
            Console.WriteLine("你输入的整数是：{0}，结果为：{1}{2}{3}{4}{5}", number, ge, shi, bai,qian,wan);
            Console.WriteLine("你输入的整数是：{0}，解密用的位数为：十位-{1}|千位-{2}，解密结果为{3}|{4}", number, shi,qian, qian*10 + shi,Convert .ToChar (qian * 10 + shi));

            Console.WriteLine("输入一个人的年龄，判断这个人是否是青年，青年的标准是18-60岁。");
            int a = Convert.ToInt32(Console.ReadLine());
            bool b = (18 <= a) && (a < 60);
            Console.WriteLine(b);

console.writeline("he")

 static int J(int n)
        {
            if (n==0)
            {
                return 1;
            }
            int res = J(n - 1) * n;
            return res;
        }
        static void test05()
        {
            int res = 1;
            for (int i = 1; i < 11; i++)
            {
                res = res * i;
            }
            Console.WriteLine(res);
        }

 static int J(int n)
        {
            if (n==0)
            {
                return 1;
            }
            int res = J(n - 1) * n;
            return res;
        }
        static void test05()
        {
            int res = 1;
            for (int i = 1; i < 11; i++)
            {
                res = res * i;
            }
            Console.WriteLine(res);
        }
 static void Main(string[] args)
        {
            //test01();
            //test02();
            //test03();
            //test04();
            //int res=F(40);
            //Console.WriteLine("res="+res);
            int res1 = J(10);
            Console.WriteLine("res1=" + res1);
            test05();

        }

static void test04()
        {
            //int num = Convert.ToInt32(Console.ReadLine());
            int f0 = 2;
            int f1 = 3;
            int n = 0;
            for (int i = 2; i < 41; i++)
            {
                n = f0 + f1;
                f0 = f1;
                f1 = n;
            }
            Console.WriteLine(n);

        }
        static int F(int n)
        {
            if (n==0)
            {
                return 2;
            }
            if (n==1)
            {
                return 3;
            }
            int res = F(n - 1) + F(n - 2);
            return res;
        }

 static bool IsSu(int number)
        {
            bool isSu = true;
            for (int j = 2; j < number-1; j++)
            {

                if (number% j == 0)
                {
                    isSu = false;
                    break;
                }
            }
            return isSu;
        }
        static int opposite(int number)//反序
        {
            int temp = number;
            int num = 0;
            while (temp % 10 != 0)//反序
            {
                num = num * 10 + temp % 10;
                temp = temp / 10;
            }     
            return num;           
        }
        static void test01()
        {
            string str = Console.ReadLine();
            string[] strArray = str.Split(' ');
            int[] intArray = new int[strArray.Length];
            for (int j = 0; j < strArray.Length; j++)
            {
                int number = Convert.ToInt32(strArray[j]);
                intArray[j] = number;
            }
            int m = intArray[0];
            int n = intArray[1];
            for (int i = m; i <= n; i++)
            {
                bool isSu =IsSu(i);
                //for (int j = 2; j < i; j++)
                //{

                //    if (i % j == 0)
                //    {
                //        issu = false;
                //        break;
                //    }
                //}
                if (isSu)
                {
                    //int temp = i;
                    //int num = 0;
                    //while (temp % 10 != 0)//反序
                    //{
                    //    num = num * 10 + temp % 10;
                    //    temp = temp / 10;
                    //}
                    int temp = i;
                    int num = opposite(temp);
                    bool isSuFan = IsSu(num);                  
                    //for (int j = 2; j < num; j++)
                    //{
                    //    if (num % j == 0)
                    //    {
                    //        isSuFan = false;
                    //        break;
                    //    }
                    //}
                    if (isSuFan == true)
                    {
                        Console.Write(i + " ");
                    }
                }              
            }           
        }

 static void test06()
        {
            string str = Console.ReadLine();
            int[] countArray = new int[26];
            for (int i = 0; i < str.Length; i++)
            {
                countArray[str[i] - 'a'] = countArray[str[i] - 'a'] + 1;
            }
            for (int i = 0; i < countArray.Length; i++)
            {
                Console.Write(countArray[i]+" ");
            }
            bool isFind = false;
            char c = ' ';
            for (int i = 0; i < str.Length; i++)
            {
                if (countArray[str[i] - 'a'] == 1)
                {
                    isFind = true;
                    c = str[i];
                    break;
                }
            }
            Console.WriteLine();
            if (isFind==false)
            {
                Console.WriteLine("no");
            }
            else
            {
                Console.WriteLine(c);
            }
            
        }

\\代表一个斜杠，即第一个\把后面那个转译了

打印“\"”, （"\\\""）,\为转译符号

打印siki说：“what is \n”, （"siki说：\"what is \\n\""）

 static void test01()
        {
            string str = Console.ReadLine();
            bool isRight = true;
            for (int i = 0; i < str.Length; i++)
            {
                if ((str[i] < '0' || str[i] > '9')&& (str[i] < 'a' || str[i] > 'z')
                    && (str[i] < 'A' || str[i] > 'Z')&& (str[i] !='_' ))//不是小写字母，不是大写字母，不是下划线,不是数字
                {
                    isRight = false;
                    break;
                }               
            }
            if (str[0] >='0'|| str[0]<='9')
            {
                isRight = false;              
            }
            if (isRight)
            {
                Console.WriteLine("是合法标识符");
            }
            else
            {
                Console.WriteLine("不是合法标识符");
            }
        }

 static void test12()
        {
            Console.WriteLine("请输入一个数组：");
            string str = Console.ReadLine();
            string[] strArray = str.Split(' ');
            int[] intArray = new int[strArray.Length];
            bool isChange = false;
            for (int i = 0; i < strArray.Length; i++)
            {
                Console.Write(strArray[i] + " ");
                int num = Convert.ToInt32(strArray[i]);
                intArray[i] = num;
            }
            for (int j = 0; j < intArray.Length-1; j++)//length-1轮比较
            {
                for (int i = 0; i < intArray.Length-1; i++)
                {
                    if (intArray[i]>intArray[i+1])
                    {
                        int temp = intArray[i];
                        intArray[i] = intArray[i + 1];
                        intArray[i + 1] = temp;
                        isChange = true;
                    }
                }
                if (isChange==false)
                {
                    break;
                }
            }
            Console.WriteLine();
            foreach (int temp in intArray)
            {
                Console.Write(temp+" ");
            }
        }

Console.ReadLine(  )

类型一致，

Convert.ToiInt32

 static void test10()
        {
            Console.WriteLine("请输入一个有序的数组：");
            string str = Console.ReadLine();
            string[] strArray = str.Split(' ');
            int[] intArray = new int[strArray.Length];
            for (int i = 0; i < strArray.Length; i++)
            {
                int num = Convert.ToInt32(strArray[i]);
                intArray[i] = num;
            }
            Console.WriteLine("请输入一个整数：");
            int n = Convert.ToInt32(Console.ReadLine());
            int m = intArray.Length-1;
            //bool find = false;//默认是未找到索引位置 m<=x<=x+1
            for (int i = 0; i < intArray.Length-1; i++)
            {                
                if (n>=intArray[i]&&n<=intArray[i+1])
                {
                    m = i;
                    //find = true;
                    break;
                }               
            }
            if (n<intArray[0])
            {
                m = -1;
            }
            int[] intArray1 = new int[intArray.Length + 1];
            for (int i = 0; i < m+1; i++)
            {
                intArray1[i] = intArray[i];
            }
            intArray1[m + 1] = n;
            for (int i = m+1; i < intArray.Length; i++)
            {
                intArray1[i+1] = intArray[i];
            }
            foreach (int temp in intArray1)
            {
                Console.Write(temp+" ");
            }

            //if (find==false)
            //{
            //    m = intArray.Length - 1;
            //}

             
        }

static void test05()
        {
            int[] arr = new int[9] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
            char[] arr1 = new char[20] { 'a','b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b' };
            float[] arr2 = new float[5] { 1.2f, 2.5f, 2.3f, 2.4f, 5.3f};
            string[] arr3 = new string[8] { "a", "b", "c", "d", "e", "f", "g", "h", };
            int[] arr4 = new int[9];
            char[] arr5 = new char[20];
            float[] arr6 = new float[5];
            string[] arr7 = new string[8];
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine(arr6[i]);
            }
            for (int i = 8; i >=0; i--)
            {
                Console.WriteLine(arr[i]);
            }
            foreach (int  temp in arr1)
            {
                Console.WriteLine(temp);
            }
            Console.WriteLine(arr.Length); 
        }
        static void test06()
        {
            string name = "missuu";
            for (int i = 0; i < name.Length; i++)
            {
                Console.Write(" " + name[i]);
            }
            Console.WriteLine();
            for (int i = name.Length-1; i >=0; i--)
            {
                Console.Write(" "+name[i]);
            }
            Console.WriteLine();
            Console.WriteLine(name.ToLower());//小写
            Console.WriteLine(name.ToUpper());//大写
            name = "  missuu  ";
            Console.WriteLine(name.TrimStart() + "|");
            Console.WriteLine(name.TrimEnd() + "|");
        }

static void test01()
        {
            for (int a = 1; a <=33; a++)
            {
                for (int b = 1; b <= 20; b++)
                {
                    for (int c = 0; c <= 50; c++)
                    {
                        if (3*a+5*b+c*2==100)
                        {
                            Console.WriteLine("a={0},b={1},c={2}",a,b,c);
                        }
                    }
                }
            }
        }

变量：不同物品不同容器盛放

浮点数：带小数的数字（包括整数，例如1.0）

结构体

struct 结构体名{

public      类型 变量名1；

⬆访问权限 类型 变量名2；

}

结构名 变量名；

变量名.变量名1=xxx；

变量名.变量名2=xxx；

枚举

定义

enum aaaa 

{

   值1，值2，值3

}

aaaa 变量名=aaaa.值x；

int name;

double jishuqi;

double pjs;

int shengao;

int zonhe;

double wendu;

using System;

namespace _0026_编程题__0_3_
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            //让⽤户输⼊两个整数，然后再输⼊0-3之间的⼀个数，0代表加法，1代表减法，2代表乘法，
            //0代表加法，1代表减法，2代表乘法，3代表除法,计算这两个数字的结果.
            Console.WriteLine("输入俩个数");
            int a = Convert.ToInt32(Console.ReadLine());
            int b = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("输入0-3之间的⼀个数，0代表加法，1代表减法，2代表乘法");
            int c = Convert.ToInt32(Console.ReadLine());
            switch (c)
            {
                case 0:
                    Console.WriteLine(a + "加" + b + "等于" + (a + b));
                    break;

                case 1:
                    Console.WriteLine(a + "减" + b + "等于" + (a - b));
                    break;

                case 2:
                    Console.WriteLine(a + "乘" + b + "等于" + (a * b));
                    break;
            }
        }
    }
}

输入语句：

• Console.ReadLine();    等待控制台输入(字符串)

输出语句：

• Console.WriteLine();    在控制台输出

数据类型转换：

• Convert.ToInt32()；

int a = Convert.ToInt32(Console.ReadLine());