求一计算公式？

Question

年租金x=10000元,租金缴费周期y=6个月，并且年租金每隔z=12个月递增k=5%如果起租时间为2013-03-26
到期时间为2016-03-29 
注：最后一笔时间误差可以在3天内。
求一共交几次钱，每次多少钱？手动算后结果：
1 2013-03-26 5000
2 2013-09-26 5000
3 2014-03-26 5250
4 2014-09-26 5250
5 2015-03-26 5512.5
6 2015-09-26 5512.5

Answer 1

double pre = 5000.0;
            Console.WriteLine(pre);
            for (int i = 1; i < 20; i++)
            {
                if (i % 2 != 0)
                {
                    Console.WriteLine(pre);
                }
                else
                {
                    pre = pre * (1 + 0.05);
                    Console.WriteLine(pre);
                }
            }          
            
            Console.Read();

Answer 2

double 年租金 = 10000;
            double 租金缴费周期 = 6;
            double 租金间隔 = 12;
            double 递增 = 0.05;
            double 租期 = 36;
            double 每期付款=0;
            double 付款周期 = 0;
            int 付款次数 = 0;
            double[] 付款数额=new double[100];
            while (付款周期 <= 租期)
            {
                if (付款周期 % 租金间隔 == 0)
                {
                    if (付款周期 != 0)
                    {
                        年租金 *= (1 + 递增);
                        每期付款 = 年租金 / 2;
                        付款数额[付款次数] = 每期付款;
                    }
                    else
                    {
                        每期付款 = 年租金 / 2;
                        付款数额[付款次数] = 每期付款;
                    }
                }
                else
                {
                    每期付款 = 年租金/2;
                    付款数额[付款次数] = 每期付款;
                }
                付款周期 += 租金缴费周期;
                付款次数++;
            }
            string rmb = "";
            for (int i = 0; i < 付款次数; i++)
            {
                rmb += " " + "第" + (i+1) + "次付款数额为:" + 付款数额[i].ToString();
            }
            MessageBox.Show(rmb);

Answer 3

随手写的  DateTime starttime = DateTime.Parse("2013-03-26");
            DateTime endtime = DateTime.Parse("2016-10-29");
            decimal d = 0m;
            decimal start = 10000;
            int count = 0, f = 0;
            bool isclear = false;
            for (DateTime midtime = starttime; midtime < endtime; midtime = midtime.AddMonths(6))
            {
                double sub = midtime.Subtract(starttime).TotalDays / 30 - 12;
                if (sub > 0)
                {
                    f++;
                    if (!isclear)
                    {
                        start = start + start * 5 / 100;
                    }
                    d = start / 2;
                    if (f != 2)//保证两次
                    {
                        isclear = true;
                    }
                    else
                    {
                        isclear = false;
                        f = 0;
                    }
                }
                else
                {
                    d = start / 2;
                }
                count++;
                Console.WriteLine("次数" + count.ToString() + "\t" + d + "\t" + midtime);
            }