2.MirrorWords

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

namespace _02.MirrorWords
{
    class Program
    {
        static void Main(string[] args)
        {
            string text = Console.ReadLine();

            string pattern = @"([@#])(?<firstword>[A-Za-z]{3,})\1{2}(?<secondword>[A-Za-z]{3,})\1";

            MatchCollection hiddenWordPairs = Regex.Matches(text, pattern);
            Dictionary<string, string> mirrorwords = new Dictionary<string, string>();
            int mirrorWordsCount = 0;

            foreach (Match wordPair in hiddenWordPairs)
            {
                string firstword = wordPair.Groups["firstword"].Value;
                string secondword = wordPair.Groups["secondword"].Value;
                string secondWordReversed = string.Empty;

                for (int i = secondword.Length - 1; i >= 0; i--)
                {
                    char current = secondword[i];
                    secondWordReversed += current;
                }
                if (firstword == secondWordReversed)
                {
                    if (!mirrorwords.ContainsKey(firstword))
                    {
                        mirrorwords.Add(firstword, secondword);
                        mirrorWordsCount++;
                    }
                }
            }
            if (hiddenWordPairs.Count == 0)
            {
                Console.WriteLine($"No word pairs found!");
            }
            else if (hiddenWordPairs.Count > 0)
            {
                Console.WriteLine($"{hiddenWordPairs.Count} word pairs found!");
            }
            if (mirrorWordsCount == 0)
            {
                Console.WriteLine($"No mirror words!");
            }
            else if (mirrorWordsCount > 0)
            {
                Console.WriteLine("The mirror words are:");

                foreach (var kvp in mirrorwords)
                {
                    Console.Write(string.Join(", ",$"{kvp.Key} <=> {kvp.Value}"));
                }
            }
        }
    }
}