using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

          string leaveSymbols = "AL,AL,AL,AL_AM";

        var dateRanges = LeaveProcessor.ProcessLeaveSymbols(leaveSymbols);

Console.WriteLine("Start");

        foreach (var range in dateRanges)

        {

            Console.WriteLine(range);

        }

    }

}

​

​

 public class LeaveProcessor

    { 

        public static List<DateRange> ProcessLeaveSymbols(string leaveSymbols)

        {

            var symbols = leaveSymbols.Split(',').Select(s => s.Trim()).ToList();

            var dateRanges = new List<DateRange>();

            var currentRange = new DateRange();

​

            for (int i = 0; i < symbols.Count; i++)

            {

                var symbol = symbols[i];

                var isLastSymbol = i == symbols.Count - 1;

​

                if (symbol == "AL")

                {

                    if (currentRange.StartDate == null)

                    {

                        currentRange.StartDate = DateTime.Today.AddDays(i);

                    }

                    currentRange.EndDate = DateTime.Today.AddDays(i);

                }

                else if (symbol == "AL_AM")

                {

                    if (currentRange.StartDate == null)

                    {

                        currentRange.StartDate = DateTime.Today.AddDays(i);

                    }

                    currentRange.EndDate = DateTime.Today.AddDays(i);

                    currentRange.EndHalfDay = HalfDay.AM;

                    dateRanges.Add(currentRange);

                    currentRange = new DateRange();

                }

                else if (symbol == "AL_PM")

                {

                    if (currentRange.StartDate != null)

                    {

                        dateRanges.Add(currentRange);

                    }

                    currentRange = new DateRange

                    {

                        StartDate = DateTime.Today.AddDays(i),

                        EndDate = DateTime.Today.AddDays(i),

                        StartHalfDay = HalfDay.PM

                    };

                    dateRanges.Add(currentRange);

                    currentRange = new DateRange();

                }

​

                if (isLastSymbol && currentRange.StartDate != null)

                {

                    dateRanges.Add(currentRange);

                }

            }

​

            return dateRanges;

        }

    }

​

    public class DateRange

    {

        public DateTime? StartDate { get; set; }

        public DateTime? EndDate { get; set; }

        public HalfDay? StartHalfDay { get; set; }

        public HalfDay? EndHalfDay { get; set; }

​

        public override string ToString()

        {

            if (StartDate == null || EndDate == null)

                return "Invalid date range";

​

            if (StartDate == EndDate)

            {

                if (StartHalfDay == HalfDay.PM)

                    return $"{StartDate:yyyy-MM-dd} PM";

                else if (EndHalfDay == HalfDay.AM)

                    return $"{StartDate:yyyy-MM-dd} AM";

                else

                    return $"{StartDate:yyyy-MM-dd}";

            }

            else

            {

                return $"{StartDate:yyyy-MM-dd} to {EndDate:yyyy-MM-dd}";

            }

        }

    }

​

    public enum HalfDay

    {

        AM,

        PM

    }

​

​

​

​

​

​