Adv2018/D18.2/Program.cs

using System;
using System.Collections.Generic;
using System.IO;

namespace D18._2
{
    class Program
    {
        enum EnumType { Open = 0, Trees, Lumber }
        static void Main(string[] args)
        {
            if (args.Length < 1) return;
            if (File.Exists(args[0]) == false) return;
            var file = File.OpenText(args[0]);

            const int size = 50;

            var map = new (EnumType type, (int o, int t, int l) adj)[size, size];
            CreateMap(file, map);

            (int o, int t, int l) count = (0, 0, 0);

            var prev = new Dictionary<(int, int, int), int>();
            var dup = new Dictionary<(int, int, int), int>();

            int minutes = 1;
            do
            {
                FillAdjacency(size, map);

                count = NextState(size, map);

                if (prev.TryGetValue(count, out int prevminute))
                {
                    if (dup.TryGetValue(count, out int dupminute))
                    {
                        var period = minutes - prevminute;
                        var leftover = minutes % period;
                        if (minutes % period == 1_000_000_000 % period)
                        {
                            // this line seems not to make the schmilblick going forward
                            // for (var i = 0; i < leftover; ++i) count = NextState(size, map);
                            break;
                        }
                    }

                    dup.TryAdd(count, minutes);
                }

                prev[count] = minutes;
            } while (minutes++ > 0);

            int result = count.l * count.t;
            Console.WriteLine($"The result is : {result}");
        }

        private static (int o, int t, int l) NextState(int size, (EnumType type, (int o, int t, int l) adj)[,] map)
        {
            (int o, int t, int l) count = (0, 0, 0);
            for (var y = 0; y < size; ++y)
            {
                for (var x = 0; x < size; ++x)
                {
                    var tile = map[y, x];
                    if (tile.type == EnumType.Open)
                    {
                        if (tile.adj.t >= 3) map[y, x].type = EnumType.Trees;
                    }

                    else if (tile.type == EnumType.Trees)
                    {
                        if (tile.adj.l >= 3) map[y, x].type = EnumType.Lumber;
                    }

                    else if (tile.type == EnumType.Lumber)
                    {
                        if (tile.adj.l >= 1 && tile.adj.t >= 1) map[y, x].type = EnumType.Lumber;
                        else map[y, x].type = EnumType.Open;
                    }

                    if (map[y, x].type == EnumType.Open) count.o++;
                    if (map[y, x].type == EnumType.Trees) count.t++;
                    if (map[y, x].type == EnumType.Lumber) count.l++;
                }
            }

            return count;
        }

        private static (int o, int t, int l) FillAdjacency(int size, (EnumType type, (int o, int t, int l) adj)[,] map)
        {
            (int o, int t, int l) count = (0, 0, 0);
            for (var y = 0; y < size; ++y)
                for (var x = 0; x < size; ++x)
                {
                    int count1 = OfType(EnumType.Open, size, map, y, x);
                    int count2 = OfType(EnumType.Trees, size, map, y, x);
                    int count3 = OfType(EnumType.Lumber, size, map, y, x);

                    var result = (count1, count2, count3);

                    map[y, x].adj = result;

                    if (map[y, x].type == EnumType.Open) count.o++;
                    if (map[y, x].type == EnumType.Trees) count.t++;
                    if (map[y, x].type == EnumType.Lumber) count.l++;
                }
            return count;
        }

        private static int OfType(EnumType type, int size, (EnumType type, (int o, int t, int l) adj)[,] map, int y, int x)
        {
            int count = 0;
            if (y > 0 && x > 0) count += map[y - 1, x - 1].type == type ? 1 : 0;
            if (y > 0) count += map[y - 1, x].type == type ? 1 : 0;
            if (y > 0 && x < size - 1) count += map[y - 1, x + 1].type == type ? 1 : 0;

            if (x > 0) count += map[y, x - 1].type == type ? 1 : 0;
            if (x < size - 1) count += map[y, x + 1].type == type ? 1 : 0;

            if (y < size - 1 && x > 0) count += map[y + 1, x - 1].type == type ? 1 : 0;
            if (y < size - 1) count += map[y + 1, x].type == type ? 1 : 0;
            if (y < size - 1 && x < size - 1) count += map[y + 1, x + 1].type == type ? 1 : 0;
            return count;
        }

        private static void CreateMap(StreamReader file, (EnumType type, (int o, int t, int l) adj)[,] map)
        {
            int y = 0;
            do
            {
                var line = file.ReadLine();
                if (line == null) break;

                int x = 0;
                foreach (var c in line)
                {
                    EnumType type;
                    switch (c)
                    {
                        case '|':
                            type = EnumType.Trees;
                            break;
                        case '#':
                            type = EnumType.Lumber;
                            break;
                        case '.':
                        default:
                            type = EnumType.Open;
                            break;

                    }

                    map[y, x] = (type, (0, 0, 0));
                    x++;
                }


                ++y;
            } while (true);
        }
    }
}