母牛生小牛问题

若母牛从其出生第四年（3周年后）开始每年都会生一头小母牛，按这个规律，1头年龄为year的母牛在futureYear个年头后会生几头母牛？

C# Code:

    class Cow

    {

        static void Main(string[] args)

        {

            for (int i = 0; i <= 10; i++)

            {

                Console.WriteLine(new Cow(0, i).SonNumber.ToString());

            }

            Console.ReadKey();

        }

        public Cow(int year, int futureYear)

        {

            this.year = year;

            this.futureYear = futureYear;

            CountSonNumber();

        }

        private int year;

        private int futureYear;

        public int SonNumber { get; private set; }

        private void CountSonNumber()

        {

            var leftYears = futureYear;

            var currentYear = year;

            SonNumber = 1;

            while (currentYear < 3)

            {

                if (leftYears > 0)

                {

                    currentYear++;

                    leftYears--;

                }

                else

                {

                    return;

                }

            }

            for (int i = 0; i <= leftYears; i++)

            {

                Cow newCow = new Cow(0,leftYears-i);

                SonNumber += newCow.SonNumber;

            }

        }

    }

 

Output:

1

1

1

2

3

4

6

9

13

19

28