C# [HOMEWORK] - STRINGS

uprajnenie v chas ///////////////



 string banList = Console.ReadLine();
            string[] parts = Console.ReadLine().Split(new[] { '@' });
            string username = parts[0]; // "hello"
            string domain = parts[1]; // "example.com"

            string replace = new string('*', username.Length);
            banList = banList.Replace(username, replace);

            Console.WriteLine(banList);

1 zadacha   ///////////////////////////////////////////////////////////////////

string text = "Elrond: Cast it into the fire! Destroy it!";
            char[] charr = text.ToCharArray();
            Array.Reverse(charr);
            Console.WriteLine(charr);



2 zadacha ///////////////////////////////////////////////////////////////////////

 Console.Write("Enter a sequence of characters with max lenght 20: ");
            string text = Console.ReadLine();
            string result = text;

            if (text.Length <= 20)
            {
                text = text.PadRight(20, '*');
                Console.WriteLine(text);
            }
            else
            {
                result = text.Substring(0, 20);
                Console.WriteLine(result);
            }


3 zadacha  ///////////////////////////////////////////////////////////////////////////////

 string text = Console.ReadLine().ToLower();
            string search = Console.ReadLine().ToLower();

            int count = text.Select((c, i) => text.Substring(i)).Count(sub => sub.StartsWith(search));

            Console.WriteLine(count);


4 zadacha ////////////////////////////////////////////////////////////////////////////

string[] banList = Console.ReadLine().Split(',').Select(b => b.Trim()).ToArray();
        string text = Console.ReadLine();
        foreach (var ban in banList)
        {
            string replace = new string('*', ban.Length);
            text = text.Replace(ban, replace);
        }
        Console.WriteLine(text);


5 zadacha /////////////////////////////////////////////////////////////////


string input = Console.ReadLine();
        foreach (var ch in input)
        {
            int num = Convert.ToInt32(ch);
            Console.Write("\\u{0:x4}", num);
        }
        Console.WriteLine();



6 zadacha //////////////////////////////////////////////////////////////////////

char[] symbols = { ',', '?', '!', '.', ' ' };
        List<string> words = Console.ReadLine().Split(symbols, StringSplitOptions.RemoveEmptyEntries).Select(p => p).ToList();
        var result = new SortedSet<string>();
        bool isPalimandor = true;
        foreach (string word in words)
        {
            isPalimandor = true;
            if (word.Length == 1)
            {
                result.Add(word);
            }
               ///////////////////////
            for (int i = 0; i < word.Length / 2; i++)
            {
                if (word[i] != word[word.Length - i - 1])
                {
                    isPalimandor = false;
                }
                if (isPalimandor == true)
                {
                   result.Add(word);
                }
            }


        }
        Console.WriteLine(string.Join(", ", result));


7 zadacha  /////////////////////////////////////////////////////////////////////////////////////

Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.InvariantCulture;
            string[] input = Console.ReadLine().Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries).ToArray();

            double sum = 0;
            for (int i = 0; i < input.Length; i++)
            {
                string fromInput = input[i];
                char before = fromInput[0];
                char after = fromInput[fromInput.Length - 1];
                double num = double.Parse(fromInput.Substring(1, fromInput.Length - 2));

                if (char.IsUpper(before))
                {
                    int beforePossition = before - 'A' + 1;
                    num /= beforePossition;
                }
                else
                {
                    int beforePossition = before - 'a' + 1;
                    num *= beforePossition;
                }
                if (char.IsUpper(after))
                {
                    int afrerPossition = after - 'A' + 1;
                    num -= afrerPossition;
                }
                else
                {
                    int afrerPossition = after - 'a' + 1;
                    num += afrerPossition;
                }
                sum += num;
            }
            Console.WriteLine("{0:f2}", sum);