AdventOfCode/2022/Day14CSharp/Program.cs

using System.Drawing;

Part01();
Part02();

void Part01()
{
    var exampleCave = new Cave("example-input.txt");
    exampleCave.PrintCave();
    int result = exampleCave.DropUntilOverflow();
    exampleCave.PrintCave();
    Console.WriteLine("Example Number of Sand: {0}", result);

    var puzzleCave = new Cave("puzzle-input.txt");
    puzzleCave.PrintCave();
    result = puzzleCave.DropUntilOverflow();
    puzzleCave.PrintCave();
    Console.WriteLine("Puzzle Number of Sand: {0}", result);
}

void Part02()
{
    var exampleCave = new Cave("example-input.txt");
    exampleCave.PrintCave();
    int result = exampleCave.DropUntilSourceIsPlugged();
    exampleCave.PrintCave();
    Console.WriteLine("Example Number of Sand: {0}", result);

    var puzzleCave = new Cave("puzzle-input.txt");
    puzzleCave.PrintCave();
    result = puzzleCave.DropUntilSourceIsPlugged();
    puzzleCave.PrintCave();
    Console.WriteLine("Puzzle Number of Sand: {0}", result);
}

class Cave
{
    public enum BlockType
    {
        None,
        Sand,
        Rock,
        SandSource
    }
    public Dictionary<Point, BlockType> CaveData = new Dictionary<Point, BlockType>();
    public Point SandSource { get; set; } = new Point(500, 0);

    public Cave(string filename)
    {
        using (StreamReader reader = System.IO.File.OpenText(filename))
        {
            while (!reader.EndOfStream)
            {
                string? line = reader.ReadLine();
                if (line == null) { throw new InvalidDataException(); }

                var vectors = line.Split("->", StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);

                Point lastPoint = ReadPoint(vectors[0]);
                for (int i = 1; i < vectors.Length; i++)
                {
                    Point nextPoint = ReadPoint(vectors[i]);
                    CaveData[nextPoint] = BlockType.Rock;

                    int dir;
                    if (lastPoint.X != nextPoint.X)
                    {
                        if (lastPoint.X < nextPoint.X)
                        {
                            dir = 1;
                        }
                        else
                        {
                            dir = -1;
                        }

                        while (lastPoint.X != nextPoint.X)
                        {
                            CaveData[lastPoint] = BlockType.Rock;
                            lastPoint.X += dir;
                        }
                    }
                    else if (lastPoint.Y != nextPoint.Y)
                    {
                        if (lastPoint.Y < nextPoint.Y)
                        {
                            dir = 1;
                        }
                        else
                        {
                            dir = -1;
                        }

                        while (lastPoint.Y != nextPoint.Y)
                        {
                            CaveData[lastPoint] = BlockType.Rock;
                            lastPoint.Y += dir;
                        }    
                    }
                    else
                    {
                        throw new InvalidDataException();
                    }
                }
            }
        }

        if (CaveData.ContainsKey(SandSource))
        {
            throw new InvalidDataException();
        }

        CaveData[SandSource] = BlockType.SandSource;
        FindBounds();
        TrueBottom = Bounds.Y + Bounds.Height + 2;
    }

    public void PrintCave()
    {
        PrintCave(new Point(-1, -1));
    }

    public void PrintCave(Point sand)
    {
        int x_min = Bounds.Left, x_max = x_min + Bounds.Width, y_min = Bounds.Top, y_max = y_min + Bounds.Height;

        for (int y = y_min; y <= y_max; y++)
        {
            for (int x = x_min; x <= x_max; x++)
            {
                var point = new Point(x, y);

                if (sand == point)
                {
                    Console.Write('o');
                } 
                else if (CaveData.ContainsKey(point))
                {
                    var item = CaveData[point];

                    if (item == BlockType.Rock)
                    {
                        Console.Write("#");
                    }
                    else if (item == BlockType.Sand)
                    {
                        Console.Write("o");
                    }
                    else if (item == BlockType.SandSource)
                    {
                        Console.Write("+");
                    }
                    else
                    {
                        throw new InvalidDataException();
                    }
                }
                else
                {
                    Console.Write('.');
                }
            }
            Console.WriteLine();
        }
    }

    public int DropUntilOverflow()
    {
        int count = 0;

        while(!DropSand()) { count++; }

        return count;
    }

    public int DropUntilSourceIsPlugged()
    {
        int count = 0;

        while (CaveData[SandSource] != BlockType.Sand)
        {
            DropSand(false);
            count++;
        }

        return count;
    }

    public bool DropSand(bool returnEarly = true, bool printEachStep = false)
    {
        Point sandPosition = new Point(SandSource.X, SandSource.Y);

        do
        {
            if (printEachStep) PrintCave(sandPosition);

            Point down = new Point(sandPosition.X, sandPosition.Y + 1);
            Point downLeft = new Point(sandPosition.X - 1, sandPosition.Y + 1);
            Point downRight = new Point(sandPosition.X + 1, sandPosition.Y + 1);

            if (!CaveData.ContainsKey(down) && down.Y != TrueBottom)
            {
                sandPosition = down;
            }
            else if (!CaveData.ContainsKey(downLeft) && downLeft.Y != TrueBottom)
            {
                sandPosition = downLeft;
            }
            else if (!CaveData.ContainsKey(downRight) && downRight.Y != TrueBottom)
            {
                sandPosition = downRight;
            }
            else
            {
                // Cant go anywhere, so need to stop
                CaveData[sandPosition] = BlockType.Sand;
                return false;
            }

            // Fell off the world
            if (!Bounds.Contains(sandPosition))
            {
                FindBounds();
                if (returnEarly)
                    return true;
            }
            
        } while (true);
    }

    private Rectangle Bounds { get; set; }
    private int TrueBottom { get; set; }

    private void FindBounds()
    {
        int x_min = int.MaxValue;
        int x_max = int.MinValue;
        int y_min = 0;              // sand always starts at 0
        int y_max = int.MinValue;

        foreach (var item in CaveData)
        {
            if (item.Value == BlockType.None) throw new InvalidDataException();

            x_min = Int32.Min(item.Key.X, x_min);
            x_max = Int32.Max(item.Key.X, x_max);
            y_min = Int32.Min(item.Key.Y, y_min);
            y_max = Int32.Max(item.Key.Y, y_max);
        }

        Bounds = new Rectangle(x_min, y_min, x_max-x_min, y_max-y_min);
    }

    private Point ReadPoint(string s)
    {
        Point p = new Point();
        var split = s.Split(',', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);

        p.X = Int32.Parse(split[0]);
        p.Y = Int32.Parse(split[1]);

        return p;
    }
}