Adv2018/D14.2/Program.cs

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

namespace D14._2
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length == 0) return;

            string inputStr = args[0];
            
            int [] input = inputStr.Select(c => c - '0').ToArray();

            int ccount = 0;
            int count = 2;

            int elf1 = 0;
            int elf2 = 1;

            var recipes = new List<int>() { 3, 7 };

            do
            {
                int nrecipe = recipes[elf1] + recipes[elf2];

                if (nrecipe < 10)
                {
                    recipes.Add(nrecipe);

                    CheckInput(input, ref ccount, ref count, nrecipe);

                }
                else
                {
                    foreach (var nr in new[] { 1, nrecipe - 10 })
                    {
                        recipes.Add(nr);

                        CheckInput(input, ref ccount, ref count, nr);

                        if (ccount == input.Length) break;
                    }
                }

                elf1 = (elf1 + 1 + recipes[elf1]) % recipes.Count;
                elf2 = (elf2 + 1 + recipes[elf2]) % recipes.Count;

            } while (ccount != input.Length);


            Console.WriteLine(count.ToString());
        }

        private static void CheckInput(int[] input, ref int ccount, ref int count, int nrecipe)
        {
            if (input[ccount] == nrecipe) ccount++;
            else if (input[0] == nrecipe)
            {
                count += ccount;
                ccount = 1;
            }
            else
            {
                count += ccount + 1;
                ccount = 0;
            }
        }
    }
}