Fordítóprogramok 2. hét gyak

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Forditok2gyak
{
    class Program
    {
        static void Main(string[] args)
        {
            string allapot = "q0";
            string s = "-12651230";
            for (int i = 0; i < s.Length && allapot != "error"; i++)
            {
                Console.WriteLine("Állapot: " + allapot + " ||| Aktuális karakter: " + s[i].ToString());
                allapot = delta(allapot, s[i]);
            }

            Console.ReadKey();
        }

        static string delta(string allapot, char s)
        {
            switch (allapot + getAllapot(s))
            {
                case "q0-": return "q1";
                case "q0+": return "q1";
                case "q0N": return "q2";
                case "q1N": return "q2";
                case "q2N": return "q2";
            }
            return "error";
        }

        static string getAllapot(char str)
        {
            if (Char.IsDigit(str)) return "N";
            return str.ToString();
        }
    }
}