using System;

using System.Text.RegularExpressions;

​

public class allstrings

{

    public static string ToSnakeCase(string str)

    {

        return Regex.Replace(str, "[A-Z]", "_$0").ToLower();

    }

    public static string ToCamelCase(string str1)

    {

        return Regex.Replace(str1, "_[a-z]", delegate (Match m) {

        return m.ToString().TrimStart('_').ToUpper();

        });

    }

    //string to camelcase

    public static void convert(String s)

    {

        int cnt = 0;

        int n = s.Length;

        char[] ch = s.ToCharArray();

        int res_ind = 0;

        for (int i = 0; i < n; i++)

        {

            if (ch[i] == ' ')

            {

                cnt++;

                ch[i + 1] = char.ToUpper(ch[i + 1]);

                continue;

            }

            else

                ch[res_ind++] = ch[i];

        }

        for (int i = 0; i < n - cnt; i++)

            Console.Write(ch[i]);

    }

    //string to snakecase

    public static void converts(string str)

    {

        int n = str.Length;

        string str1 = "";

​

        for (int i = 0; i < n; i++)

        {

            if (str[i] == ' ')

                str1 = str1 + '_';

            else

                str1 = str1 +

                Char.ToLower(str[i]);

        }

        Console.Write(str1);

    }

    public static void Main(string[] args)

    {

        Console.WriteLine("Enter the camelcase string");

     x: string s = Console.ReadLine();

        if (string.IsNullOrEmpty(s))

        {

            Console.WriteLine("null values are not to be given");

            goto x;          

        }   

        else if (Regex.IsMatch(s, "[A-Z]"))

        {

        Console.WriteLine(ToSnakeCase(s));

        }

        else

        {

        Console.WriteLine("invalid string");

        goto x;

        }

        Console.WriteLine("Enter the snakecase string");

    y:  string v = Console.ReadLine();

        if (string.IsNullOrEmpty(v))

        {

            Console.WriteLine("null values are not to be given");

            goto y;

        }

       else if (Regex.IsMatch(v, "_"))

       {

            Console.WriteLine(ToCamelCase(v));

        }

       else

       {

            Console.WriteLine("invalid string");

            goto y;         

        }

        Console.WriteLine("enter the string that converts to camelcase");

     z: String a = Console.ReadLine();

        if (string.IsNullOrEmpty(a))

        {

            Console.WriteLine("null values are not to be given");

            goto z;

        }

        else if(Regex.IsMatch(a, " "))

        {

            converts(a);

        }

        else

        {

            Console.WriteLine("invalid");

            goto z;

        }

        Console.ReadLine();

        Console.WriteLine("Enter the string that converts to snakecase");

    k:  string b = Console.ReadLine();

        if (string.IsNullOrEmpty(b))

        {

            Console.WriteLine("null values are not accepted");

           goto k;

        }

        else if (Regex.IsMatch(b, " "))

        {

            convert(b);

        }

        else

        {

            Console.WriteLine("invalid string");

            goto k;

        }

           Console.ReadLine();

    }

}

​

​

​

​

​

​

​