//Rextester.Program.Main is the entry point for your code. Don't change it.

//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

​

using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Text;

​

namespace Rextester

{

    public class Program

    {

        //common start for all three methods here -- pull it out to help with potential benchmarking later

        public static string PreProcess(string input)

        {

            byte[] r = Convert.FromBase64String(input);

            return BitConverter.ToString(r);

        } 

        public static string Original(string input)

        {       

            string c = input.Replace("-", string.Empty);

            string h = c.Replace("A", "K").Replace("B", "L").Replace("C", "M").Replace("D", "N").Replace("E", "O")

                .Replace("F", "P").Replace("0", "A").Replace("1","B").Replace("2", "C").Replace("3", "D").Replace("4", "E")

                .Replace("5", "F").Replace("6", "G").Replace("7", "H").Replace("8", "I")

                .Replace("9", "J");

            return h.ToLower();

        }

        private static Dictionary<char, char> map = new Dictionary<char, char> {

            {'A', 'k'}, {'B', 'l'}, {'C', 'm'}, {'D', 'n'}, {'E', 'o'}, {'F', 'p'},

            {'0', 'a'},{'1', 'b'}, {'2', 'c'}, {'3', 'd'},{'4', 'e'}, {'5', 'f'},

            {'6', 'g'},{'7', 'h'},{'8', 'i'}, {'9', 'j'}

        };

        public static string NewOption1(string input)

        {

            return string.Create(2*(input.Length+1)/3 , input, (r, d) => {

                int j = 0;

                foreach(char c in d)

                {   

                    if (c == '-') continue;

                    r[j++] = map[c];

                }

            });

        }

        public static string NewOption2(string input)

        {

            var result = new StringBuilder(2*(input.Length+1)/3);

            foreach(char c in input)

            {

                if (c == '-') continue;

                result.Append(map[c]);

            }

            return result.ToString();

        }

        public static void Main(string[] args)

        {

            // always in the form AA-BB-CC etc

            string input = PreProcess("XFEWtnopccImhpHTzGeoeXBg4ws=");          

            string temp = "90-17-23-09-42-33"; //random, used to force JIT of methods so JIT won't pollute stopwatch times;

            string o0 = Original(temp);

            string o1 = NewOption1(temp);

            string o2 = NewOption2(temp);

            var watcher = Stopwatch.StartNew();

            o0 = Original(input);

            watcher.Stop();

            var t0 = watcher.ElapsedTicks;

            watcher = Stopwatch.StartNew();

            o1 = NewOption1(input);

            watcher.Stop();

            var t1 = watcher.ElapsedTicks;      

            watcher = Stopwatch.StartNew();

            o2 = NewOption2(input);

            watcher.Stop();

            var t2 = watcher.ElapsedTicks;

​

            Console.WriteLine($"Original Time: {t0,5}\tResult: {o0}");

            Console.WriteLine($"Option 1 Time: {t1,5}\tResult: {o1}");

            Console.WriteLine($"Option 2 Time: {t2,5}\tResult: {o2}");

        }

    }

}