Advent of Code: Day 13 Solution

public static class AoCDay13
{
    /// <summary>
    /// Fold along the x axis given the y coordinate.
    /// </summary>
    /// <param name="_points"></param>
    /// <param name="_y"></param>
    /// <param name="_height"></param>
    public static Point[] FoldX(Point[] _points, int _y)
    {
        HashSet<Point> _pointsList = new HashSet<Point>();
        foreach (var _point in _points)
        {
            if (_point.Y > _y)
            {
                Point _p = new Point(_point.X, _y + -(_point.Y - _y));
                _pointsList.Add(_p);
            }
            else
            {
                _pointsList.Add(new Point(_point.X, _point.Y));
            }
        }
        return _pointsList.ToArray();
    }

    /// <summary>
    /// Fold along the x axis given the y coordinate.
    /// </summary>
    /// <param name="_points"></param>
    /// <param name="_y"></param>
    /// <param name="_height"></param>
    public static Point[] FoldY(Point[] _points, int _x)
    {
        HashSet<Point> _pointsList = new HashSet<Point>();

        foreach (var _point in _points)
        {
            if (_point.X > _x)
            {
                Point _p = new Point(_x + -(_point.X - _x), _point.Y);
                _pointsList.Add(_p);
            }
            else
            {
                _pointsList.Add(new Point(_point.X, _point.Y));
            }
        }
        return _pointsList.ToArray();
    }

    public static Point[] Fold(Point[] _points, char _axis, int _value)
    {
        switch (_axis)
        {
            case 'x':
                return FoldY(_points, _value);
                break;
            case 'y':
                return FoldX(_points, _value);
            default:
                return _points;
        }
    }

    public static void Draw(Point[] _points, ref StringBuilder _sb, int _width, int _height)
    {
        for (int _y = 0; _y < _height / 10; _y++)
        {
            for (int _x = 0; _x < _width / 10; _x++)
            {
                Point _point = new Point(_x, _y);
                if (_points.Contains(_point))
                    Console.Write("#");
                else
                {
                    Console.Write(" ");
                }
                // So many new lines makes the text shoot up too quick so delay it.
                // Plus, it looks cool =D
                Thread.Sleep(15);
            }
            Console.WriteLine("");
        }
    }

    public static (T[] _first, T[] _second) Split<T>(this T[] array, Func<T[], int> _func) {
        return (array.Take(_func(array)).ToArray(), array.Skip(_func(array)).ToArray());
    }

    public static void Main(string[] _args)
    {
        // var _points =
        //     "6,10\n0,14\n9,10\n0,3\n10,4\n4,11\n6,0\n6,12\n4,1\n0,13\n10,12\n3,4\n3,0\n8,4\n1,10\n2,14\n8,10\n9,0"
        //     .Split('\n')
        //     .Select(_s => _s.Split(','))
        //     .Select(_strings => new Point(int.Parse(_strings[0]), int.Parse(_strings[1])))
        //     .ToArray();

        var (_points, _instructionSet) = File.ReadAllLines("D:\\Projects\\AoC\\AoC\\AoCDay13.txt")
            .Split(_strings => _strings.ToList().IndexOf(_strings.First(string.IsNullOrWhiteSpace)));

        var _puzzlePoints =
            _points
            .Select(_s => _s.Split(','))
            .Select(_strings => new Point(int.Parse(_strings[0]), int.Parse(_strings[1])))
            .ToArray();

        var _instructions =
            _instructionSet
            .Where(_s => !string.IsNullOrWhiteSpace(_s))
            .Select(_s => new {_axis = _s.Split('=')[0].Last(), _value = int.Parse(_s.Split('=')[1])});

        int _width = _puzzlePoints.Select(_point => _point.X).Concat(new[] {int.MinValue}).Max();
        int _height = _puzzlePoints.Select(_point => _point.Y).Concat(new[] {int.MinValue}).Max();

        foreach (var _instruction in _instructions)
        {
            _puzzlePoints = Fold(_puzzlePoints, _instruction._axis, _instruction._value);
        }

        Console.WriteLine($"Points Count: {_puzzlePoints.Length}");
        StringBuilder _sb = new StringBuilder();
        Draw(_puzzlePoints, ref _sb, _width, _height);
    }
}