Adv2016/D10.1/Program.cs

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

namespace D10._1
{
    public class Bot
    {
        public int ID { get; }
        private int? M1;
        private int? M2;

        public Bot(int id) => ID = id;

        public bool IsFull() => M1.HasValue && M2.HasValue;

        public void Take(int m)
        {
            if (M1.HasValue == false) M1 = m;
            else if (M2.HasValue == false) M2 = m;
            else throw new Exception();
        }

        public int GiveLowest()
        {
            if (M1.HasValue == false && M2.HasValue == false) throw new Exception();
            if (M1.HasValue == false && M2.HasValue == true ||
                M2 < M1)
            {
                int r = M2.Value;
                M2 = null;
                return r;
            }
            if (M1.HasValue == true && M2.HasValue == false ||
                M1 < M2)
            {
                int r = M1.Value;
                M1 = null;
                return r;
            }
            throw new Exception();
        }

        public int GiveHighest()
        {
            if (M1.HasValue == false && M2.HasValue == false) throw new Exception();
            if (M1.HasValue == false && M2.HasValue == true ||
                M2 > M1)
            {
                int r = M2.Value;
                M2 = null;
                return r;
            }
            if (M1.HasValue == true && M2.HasValue == false ||
                M1 > M2)
            {
                int r = M1.Value;
                M1 = null;
                return r;
            }
            throw new Exception();
        }

        public override bool Equals(object obj) => obj is Bot bot && ID == bot.ID;

        public override int GetHashCode() => HashCode.Combine(ID);
    }

    public class Program
    {
        static void Main(string[] args)
        {
            if (args.Length < 1) throw new ArgumentException();
            if (File.Exists(args[0]) == false) throw new FileNotFoundException();

            var bots = new Dictionary<int, Bot>();
            var instructions = new Dictionary<Bot, ((int, Bot low), (int, Bot high))>();

            ParseFile(args, bots, instructions);

            while (true)
            {
                var bot = bots.FirstOrDefault(b => b.Value.IsFull()).Value;
                if (bot == null) break;

                var lowest = bot.GiveLowest();
                var highest = bot.GiveHighest();

                if (lowest == 17 && highest == 61)
                {
                    Console.WriteLine($"The answer is : {bot.ID}");
                    break;
                }

                var ((_, low), (_, high)) = instructions[bot];

                low?.Take(lowest);
                high?.Take(highest);
            }
        }

        public static void ParseFile(string[] args, Dictionary<int, Bot> bots, Dictionary<Bot, ((int, Bot) low, (int, Bot high))> instructions)
        {
            var valueReg = new Regex(@"value (?<m>\d+) goes to bot (?<b>\d+)");
            var otherReg = new Regex(@"bot (?<b>\d+) gives low to (?<lt>output|bot) (?<lb>\d+) and high to (?<ht>output|bot) (?<hb>\d+)");

            using (var file = File.OpenText(args[0]))
            {
                while (true)
                {
                    var line = file.ReadLine();
                    if (line == null) break;

                    if (line.StartsWith("value "))
                    {
                        var r = valueReg.Match(line);

                        var botId = int.Parse(r.Groups["b"].Value);
                        var value = int.Parse(r.Groups["m"].Value);

                        Bot bot = TryAddBot(bots, botId);
                        bot.Take(value);
                    }
                    else
                    {
                        var r = otherReg.Match(line);

                        var botId = int.Parse(r.Groups["b"].Value);
                        var lbotId = int.Parse(r.Groups["lb"].Value);
                        var lType = r.Groups["lt"].Value;
                        var hbotId = int.Parse(r.Groups["hb"].Value);
                        var hType = r.Groups["ht"].Value;

                        ((int, Bot bot) low, (int, Bot bot) high) instr = ((lbotId, null), (hbotId, null));
                        if (lType == "bot")
                        {
                            Bot lbot = TryAddBot(bots, lbotId);
                            instr.low.bot = lbot;
                        }
                        if (hType == "bot")
                        {
                            Bot hbot = TryAddBot(bots, hbotId);
                            instr.high.bot = hbot;
                        }

                        Bot bot = TryAddBot(bots, botId);

                        instructions.Add(bot, instr);
                    }
                }
            }
        }

        private static Bot TryAddBot(Dictionary<int, Bot> bots, int botId)
        {
            Bot bot;
            if (bots.ContainsKey(botId)) bot = bots[botId];
            else
            {
                bot = new Bot(botId);
                bots.Add(botId, bot);
            }

            return bot;
        }
    }
}