Files

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace _04_04_Files
{
    class Files
    {
        static void Main(string[] args)
        {
            // 100% from the very first time!
            Regex rootPattern = new Regex(@"^(?<root>.+?)\\");
            Regex namePattern = new Regex(@"^.*\\(?<fileName>.+\..+?)$");
            Dictionary<string, Dictionary<string, long>> files = new Dictionary<string, Dictionary<string, long>>();
            long n = long.Parse(Console.ReadLine());

            for (long i = 0; i < n; i++)
            {
                string[] data = Console.ReadLine()
                .Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries);

                string path = data[0];
                long size = long.Parse(data[1]);
                string rootName = rootPattern.Match(path).Groups["root"].Value;
                string fileName = namePattern.Match(path).Groups["fileName"].Value;

                if (!files.ContainsKey(rootName))
                {
                    files.Add(rootName, new Dictionary<string, long>());
                }
                if (!files[rootName].ContainsKey(fileName))
                {
                    files[rootName].Add(fileName, 0);
                }
                files[rootName][fileName] = size;
            }

            string[] query = Console.ReadLine()
                .Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
            string extension = query[0];
            string root = query[2];

            if (!files.ContainsKey(root))
            {
                Console.WriteLine("No");
            }
            else
            {
                Dictionary<string, long> queryFiles = files[root].Where(x => x.Key.EndsWith(extension)).ToDictionary(x => x.Key, x => x.Value);
                if (queryFiles.Count == 0)
                {
                    Console.WriteLine("No");
                }
                else
                {
                    foreach (KeyValuePair<string, long> file in queryFiles.OrderByDescending(x => x.Value).ThenBy(x => x.Key))
                    {
                        Console.WriteLine($"{file.Key} - {file.Value} KB");
                    }
                }
            }
        }
    }
}