using System;

using System.Text;

using System.Linq;

using System.Collections.Generic;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        string myString = "I do not like green eggs and ham";

        Console.WriteLine($"{reverseByChar(myString)}");

        Console.WriteLine($"{MyReverse(myString)}");

    }

    //#4a - My Solution

    public static string reverseByChar(string str)

    {

        Console.WriteLine(str);

        //if (str==null) {return null;};

        // Above should have been

        if (str.Length == 1)

        {

            return str;

        }

        //return reverseByChar($"{str.Substring(1)}{str[0]}");

        return reverseByChar(str.Substring(1)) + str[0]; // should have been

    }

    //#4b - My Solution

    public static string reverseByWord(string str)

    {

        Console.WriteLine(str);

        return null;

    }

    public static string reverseByChar2(String str)

    {

        if (str == null || str.Length <= 1) {return null;}

        Console.WriteLine(str);

​

        Console.Write(str[str.Length-1]);

        return reverseByChar2(str.Substring(0,(str.Length-1)));

    }

    public static string MyReverse(string s)

    {

        if (s.Length == 1)

        {

            return s;

        }

        var firstLetter = s[0];

        return MyReverse(s.Substring(1)) + firstLetter;

    }

}