AdventOfCode Day 18 2017

   public class Duet
    {
        private Dictionary<char, long> dictionary = new Dictionary<char, long>();

        private BlockingCollection<long> que = new BlockingCollection<long>();

        private long lastSound = 0;

        public long this[string i]
        {
            get
            {
                if (char.IsDigit(i.Last()))
                {
                    return int.Parse(i);
                }
                else
                {
                    if (i.Length > 1) throw new NotImplementedException();

                    if (!dictionary.ContainsKey(i[0]))
                        this.dictionary.Add(i[0], 0);

                    return this.dictionary[i[0]];
                }
            }
            set
            {
                if (i.Length > 1) throw new NotImplementedException();
                if (!dictionary.ContainsKey(i[0]))
                    this.dictionary.Add(i[0], 0);

                this.dictionary[i[0]] = value;
            }
        }

        public void Solve()
        {
            var cmds = Properties.Resources.TextFile1.Split('\n').Select(x => x.Trim().Split(' ')).ToArray(); ;
            var answerA = Commands(cmds);

            var d1 = new Duet();
            d1["p"] = d1["0"];

            var d2 = new Duet();
            d2["p"] = d2["1"];

            var t1 = new Task<long>(() => d1.Commands2(cmds.ToArray(), d2));
            var t2 = new Task<long>(() => d2.Commands2(cmds.ToArray(), d1));

            t1.Start();
            t2.Start();

            Task.WaitAll(t1, t2);

            var answerB = t2.Result;
        }

        public long Commands(string[][] cmds)
        {
            for (int i = 0; i < cmds.Length;)
            {
                var split = cmds[i];
                switch (split[0])
                {
                    case "snd":
                        lastSound = this[split[1]];
                        break;
                    case "set":
                        this[split[1]] = this[split[2]];
                        break;
                    case "add":
                        this[split[1]] += this[split[2]];
                        break;
                    case "mul":
                        this[split[1]] *= this[split[2]];
                        break;
                    case "mod":
                        this[split[1]] %= this[split[2]];
                        break;
                    case "rcv":
                        if (this[split[1]] != 0)
                            return lastSound;
                        break;
                    case "jgz":
                        if(split[1] == "1")
                        { }
                        if (this[split[1]] > 0)
                        {
                            i += int.Parse(split[2]);
                            continue;
                        }
                        break;
                }
                i++;
            }
            throw new NotImplementedException();
        }

        public long Commands2(string[][] cmds, Duet partner)
        {
            long sndCount = 0;

            for (long i = 0; i < cmds.Length;)
            {
                var split = cmds[i];
                switch (split[0])
                {
                    case "snd": partner.que.Add(this[split[1]]); sndCount++; break;
                    case "set": this[split[1]]  = this[split[2]]; break;
                    case "add": this[split[1]] += this[split[2]]; break;
                    case "mul": this[split[1]] *= this[split[2]]; break;
                    case "mod": this[split[1]] %= this[split[2]]; break;
                    case "rcv":
                        if (que.TryTake(out long tmp, 100))
                        {
                            this[split[1]] = tmp;
                        }
                        else
                        {
                            partner.que.CompleteAdding();
                            return sndCount;
                        }
                        break;
                    case "jgz":
                        if (this[split[1]] > 0)
                        {
                            i += this[split[2]];
                            continue;
                        }
                        break;
                }
                i++;
            }
            throw new NotImplementedException();
        }