几个函数小练习

 class Program
    {
        /// <summary>
        /// 100以内与7有关的数字
        /// </summary>
        public void shuzi()
        {
            for (int i = 1; i <= 100; i++)
            {
                if (i % 10 == 7 || i / 10 == 7 || i % 7 == 0)
                {
                    Console.Write(i + "	");
                }
            }
        }
        /// <summary>
        /// 闯关分数
        /// </summary>
        /// <param name="a"></param>
        /// <returns></returns>
        public int chuangguan(int a)
        {
            int sum = 0;
            for (int i = 0; i <= a; i++)
            {
                if (i <= 20)
                {
                    sum += i;
                }
                else if (i > 20 && i <= 30)
                {
                    sum += 10;
                }
                else if (i > 30 && i <= 40)
                {
                    sum += 20;
                }
                else if (i > 40 && i < 50)
                {
                    sum += 30;
                }
                else
                {
                    sum += 100;
                }
            }
            return sum;
        }
        /// <summary>
        /// 9*9乘法表
        /// </summary>
        public void chengfabiao()
        {
            for (int i = 1; i < 10; i++)
            {
                for (int l = 1; l <= i; l++)
                {
                    Console.Write(l + "*" + i + "=" + (i * l) + "	");
                }
                Console.WriteLine();
            }
        }
        /// <summary>
        /// 100以内奇数和
        /// </summary>
        /// <returns></returns>
        public int jishu()
        {
            int sum = 0;
            for (int i = 1; i < 100; i += 2)
            {
                sum += i;
            }
            return sum;
        }
        /// <summary>
        /// 凑钱
        /// </summary>
        public void qian()
        {
            int sum = 0;
            for (int i = 0; i <= 60; i++)
            {
                for (int l = 0; l <= 30; l++)
                {
                    for (int j = 0; j <= 12; j++)
                    {
                        if (i + l * 2 + j * 5 == 60)
                        {
                            sum++;
                            Console.WriteLine("第" + sum + "种打法：需要{0}个一毛的，{1}个两毛的，{2}个五毛的。", i, l, j);
                        }
                    }
                }
            }
            Console.Write("共有" + sum + "种打法。");
        }
        /// <summary>
        /// 求方程
        /// </summary>
        /// <param name="a"></param>
        /// <returns></returns>
        public double fangcheng(double a)
        {
            double y;
            if (a < 1)
            {
                y = a;
            }
            else if (a >= 1 && a < 10)
            {
                y = 2 * a - 1;
            }
            else
            {
                y = 3 * a - 11;
            }
            return y;
        }
        /// <summary>
        /// 每个学生的平均分   
        /// </summary>
        /// <param name="a"></param>
        public void renpingjun(double[,] a)
        {
            double[,] fenshu = new double[10, 5];
            fenshu = a;
            for (int i = 0; i < 10; i++)
            {
                double sum = 0;
                for (int l = 0; l < 5; l++)
                {
                    sum += fenshu[i, l];
                }
                Console.WriteLine("第" + (i + 1) + "个同学的平均分为：" + sum / 5);
            }
        }
        /// <summary>
        /// 每科的平均分
        /// </summary>
        /// <param name="a"></param>
        public void kepingjun(double[,] a)
        {
            double[,] fenshu = new double[10, 5];
            fenshu = a;
            for (int i = 0; i < 5; i++)
            {
                double sum = 0;
                for (int l = 0; l < 10; l++)
                {
                    sum += fenshu[l, i];
                }
                Console.WriteLine("第" + (i + 1) + "科的成绩为：" + sum / 10);
            }
        }
        /// <summary>
        /// 最高分最低分
        /// </summary>
        /// <param name="a"></param>
        public void daxiao(double[,] a)
        {
            double[,] fenshu = new double[10, 5];
            fenshu = a;
            double zhong;
            double[] max = new double[5];
            double[] min = new double[5];
            for (int b = 0; b < 5; b++)
            {
                for (int l = 0; l < 10; l++)
                {
                    for (int j = 0; j < l; j++)
                    {
                        if (fenshu[l, b] < fenshu[j, b])
                        {
                            zhong = fenshu[l, b];
                            fenshu[l, b] = fenshu[j, b];
                            fenshu[j, b] = zhong;
                        }
                    }
                }
                max[b] = fenshu[9, b];
                min[b] = fenshu[0, b];
            }
            for (int i = 0; i < 5; i++)
            {
                if (max[0] < max[i])
                {
                    max[0] = max[i];
                }
            }
            Console.WriteLine("最高分为：" + max[0]);
            for (int i = 0; i < 5; i++)
            {
                if (min[0] > min[i])
                {
                    min[0] = min[i];
                }
            }
            Console.WriteLine("最低分为：" + min[0]);
        }
        /// <summary>
        /// 求最高分最低分（简单方法）
        /// </summary>
        /// <param name="a"></param>
        public void daxiao2(double[,] a)
        {
            double[,] fenshu = new double[10, 5];
            fenshu = a;
            for (int i = 0; i < 10; i++)
            {
                for (int l = 0; l < 5; l++)
                {
                    if (fenshu[0, 0] < fenshu[i, l])
                    {
                        fenshu[0, 0] = fenshu[i, l];
                    }
                }
            }
            Console.WriteLine("最高分为：" + fenshu[0, 0]);
            for (int i = 0; i < 10; i++)
            {
                for (int l = 0; l < 5; l++)
                {
                    if (fenshu[0, 0] > fenshu[i, l])
                    {
                        fenshu[0, 0] = fenshu[i, l];
                    }
                }
            }
            Console.WriteLine("最低分为：" + fenshu[0, 0]);
        }
        /// <summary>
        /// 方差           
        /// </summary>
        /// <param name="a"></param>
        /// <returns></returns>
        public double[] fangcha(double[,] a)
        {
            double[,] fenshu = new double[10, 5];
            double[] pingjun = new double[10];
            fenshu = a;
            for (int i = 0; i < 10; i++)
            {
                double sum = 0;
                for (int l = 0; l < 5; l++)
                {
                    sum += fenshu[i, l];
                }
                pingjun[i] = sum / 5;
            }
            return pingjun;
        }
        /// <summary>
        /// 判断是否是闰年
        /// </summary>
        /// <param name="a"></param>
        public void shijian(int a)
        {
            if ((a % 4 == 0 && a % 100 != 0) || a % 400 == 0)
            {
                Console.WriteLine("是闰年");
            }
            else
            {
                Console.WriteLine("不是闰年");
            }//判断闰年
        }
        //public int a;//变量可以定义在外面，类似结构体。
        static void Main(string[] args)
        {
            #region 练习
            //Program pro = new Program();
            //pro.a = int.Parse ( Console.ReadLine());



            ////练习  找出100以内与7有关的数并打印
            //Program hanshu = new Program();
            //hanshu.shuzi();



            ////练习  一个游戏，前20关是每一关自身的分数，
            ////21-30关每一关是10分
            ////31-40关，每一关是20分
            ////41-49关，每一关是30分
            ////50关，是100分
            ////输入你现在闯到的关卡数，求你现在拥有的分数
            //for (; ; )
            //{
            //    Console.Write("请输入关卡数：");
            //    int a = int.Parse(Console.ReadLine());
            //    if (a >= 0 && a < 51)
            //    {
            //        Program hanshu = new Program();
            //        Console.Write(hanshu.chuangguan(a));
            //        break;
            //    }
            //    else
            //    {
            //        Console.WriteLine("输入错误，请重新输入！");
            //    }
            //}



            ////打印99乘法表
            //Program hanshu = new Program();
            //hanshu.chengfabiao();



            ////100以内奇数和
            //Program hanshu = new Program();
            //Console.Write(hanshu.jishu());



            ////有1分钱，2分钱，5分钱硬币，要组合出6毛钱，有几种组合方式，怎样组合
            //Program hanshu = new Program();
            //hanshu.qian();



            ////有一组函数：y = x (x<1)；y = 2x -1  (1<=x<10)； y = 3x-11  (x>=10)。
            ////括号内是x的满足条件。
            ////实现功能，随意输入一个x值，输出y的值。
            //Console.Write("请输入X值：");
            //double a = double.Parse(Console.ReadLine());
            //Program hanshu = new Program();
            //Console.Write(hanshu.fangcheng(a));


            #endregion
            #region  一个麻烦的练习
            //输入十个学生5门课的成绩，分别用函数实现下列功能
            //1.计算每个学生的平均分
            //2.计算每门课的平均分
            //3.找出所有50个分数中的最高分和最低分
            //4.计算平均分方差（1/n(x1+……+x10)^2-(x1+……+x10/n)^2   xi为某一学生的平均分）
            double[,] fenshu = new double[10, 5];

            for (int i = 0; i < 10; i++)
            {
                for (int l = 0; l < 5; l++)
                {
                    Console.Write("请输入第" + (i + 1) + "个学生的第" + (l + 1) + "科成绩：");
                    fenshu[i, l] = double.Parse(Console.ReadLine());
                }
            }
            Program hanshu = new Program();
            hanshu.renpingjun(fenshu);//每个学生的平均分
            hanshu.kepingjun(fenshu);//每科的平均分
            hanshu.daxiao(fenshu);//求最大最小分
            hanshu.daxiao2(fenshu);//求最大最小简单方法 
            double[] fangcha = new double[10];
            fangcha = hanshu.fangcha(fenshu);
            double sum = 0;
            for (int i = 0; i < 10; i++)
            {
                sum += fangcha[i];
            }
            double pingjunfangcha = (0.1 * sum * sum) - (sum / 10) * (sum / 10);
            Console.WriteLine("平均分方差="+pingjunfangcha);
            #endregion

            ////1、输入年月日，看输入的日期是否正确
            ////2、输出是今年是否是闰年（29天），输出日期
            ////   闰年的判断普通年能被4整除且不能被100整除的为闰年,整百的年份能被400整除
            ////3、输出是今年的第几天
            ////   输入年，看年份是否正确，年（0-9999）

            //for (; ; )
            //{
            //    try
            //    {
            //        Console.Write("请输入日期：");
            //        DateTime a =      DateTime.Parse(Console.ReadLine());
            //        int b = a.Year;
            //        Program hanshu = new Program();
            //        hanshu.shijian(b);
            //        Console.WriteLine(a.DayOfYear);//输出第几天
            //        break;
            //    }
            //    catch
            //    {
            //        Console.WriteLine("您的输入有误！请重新输入！");
            //    }
            //}



            Console.ReadLine();
        }
    }