using System;

using System.Text.RegularExpressions;

public class ByRegexParser

{

    public int GetDigitsCount(string input)

    {

        var regex = new Regex(@"\d");

        int count = regex.Matches(input).Count;

        return count;

    }

}

​

public class ByCharParser

{

    public int GetDigitsCount(string input)

    {

        int count = 0;

        foreach(char c in input)

        {

            if(c > 47 && c < 58)

                count ++;

        }

        return count;

    }

}

​

public class DigitsCountParser

{

    public int GetDigitsCount(string input, string type)

    {

        if(type == "regex")

        {

            return new ByRegexParser().GetDigitsCount(input);

        }

        else if(type == "char")

        {

            return new ByCharParser().GetDigitsCount(input);    

        }

        return 0;

    }

}

​

public class Program

{

    public static void Main(string []args)

    {

        string input = "hello09";

        string type = "regex";

        Console.WriteLine(new DigitsCountParser().GetDigitsCount(input, type));

        type = "char";

        Console.WriteLine(new DigitsCountParser().GetDigitsCount(input, type));

    }

}