using System;

using System.Collections.Generic;

using System.Globalization;

using System.Linq;

public class Program

{

    public static void Main()

    {

            var input = @"photo.jpg, Warsaw, 2013-09-05 14:08:15

john.png, London, 2015-06-20 15:13:22

myFriends.png, Warsaw, 2013-09-05 14:07:13

Eiffel.jpg, Paris, 2015-07-23 08:03:02

pisatower.jpg, Paris, 2015-07-22 23:59:59

BOB.jpg, London, 2015-08-05 00:02:03

notredame.png, Paris, 2015-09-01 12:00:00

me.jpg, Warsaw, 2013-09-06 15:40:22

a.png, Warsaw, 2016-02-13 13:33:50

b.jpg, Warsaw, 2016-01-02 15:12:22

c.jpg, Warsaw, 2016-01-02 14:34:30

d.jpg, Warsaw, 2016-01-02 15:15:01

e.png, Warsaw, 2016-01-02 09:49:09

f.png, Warsaw, 2016-01-02 10:55:32

g.jpg, Warsaw, 2016-02-29 22:13:11";

            var output = @"Warsaw02.jpg

London1.png

Warsaw01.png

Paris2.jpg

Paris1.jpg

London2.jpg

Paris3.png

Warsaw03.jpg

Warsaw09.png

Warsaw07.jpg

Warsaw06.jpg

Warsaw08.jpg

Warsaw04.png

Warsaw05.png

Warsaw10.jpg";

            var resultQ3 = Solution_Q3(input);

​

            Console.WriteLine("\n\tResult:\n{0}\n\n\tExpected:\n{1}", resultQ3, output);

    }

​

    public static string Solution_Q3(string S)

    {

        const string DateTimeFormat = "yyyy-MM-dd HH:mm:ss";

​

        var lines = S.Split('\n');

        //Item1: order

        //Item2 3: extension

        //Item3 4: cityName

        //Item4 5: datetime(yyyy-MM-DD HH:mm:ss)

        var items = new List<Tuple<int, string, string, DateTime>>();

        var results = new Dictionary<int, string>();

​

        // Gather data

        for (int index = 0; index < lines.Length; index++)

        {

            var line = lines[index];

            var blocks = line.Split(',').Select(z => z.Trim()).ToArray();

            var filenameSplits = blocks[0].Split('.');

​

            var extension = filenameSplits[1].Trim();

            var cityName = TrimAndClean(blocks[1], 20);

            var dateTime = DateTime.ParseExact(blocks[2], DateTimeFormat, CultureInfo.InvariantCulture).ToUniversalTime();

​

            items.Add(Tuple.Create(index, extension, cityName, dateTime));

        }

​

        // Gather Counts

        var groups = items

            .OrderBy(z => z.Item4)

            .GroupBy(z => z.Item3);

        foreach (var groupItem in groups)

        {

            var counter = 1;

            foreach (var item in groupItem)

            {

                var counterString = new string('0', groupItem.Count().ToString().Length);

                var filename = string.Format("{0}{1}.{2}", item.Item3, counter.ToString(counterString), item.Item2);

​

                results.Add(item.Item1, filename);

                counter++;

            }

        }

​

        var returnResults = results

            .OrderBy(z => z.Key)

            .Select(z => z.Value)

            .ToArray();

        return string.Join("\n", returnResults);

    }

​

    private static string TrimAndClean(string s, int nrChars)

    {

        var trimmed = s.Trim().ToLowerInvariant();

        var maxLen = Math.Min(trimmed.Length, nrChars);

​

        var text = Char.ToUpperInvariant(trimmed[0]) + trimmed.Substring(1, maxLen - 1);

​

        return text;

    }

}

​