AOC2021_05_2

List<Direction> directions = new List<Direction>();
List<int> xStarts = new List<int>();
List<int> xFinishes = new List<int>();
List<int> yStarts = new List<int>();
List<int> yFinishes = new List<int>();

int[,] grid;
List<Tuple<int, int>> intersections = new List<Tuple<int, int>>();

void Main()
{
    var input = File.ReadAllLines(@"C:\Users\dostj\Documents\LINQPad Queries\AdventOfCode\2021\05.txt");
    //input = File.ReadAllLines(@"C:\Users\dostj\Documents\LINQPad Queries\AdventOfCode\2021\05_test.txt");

    foreach (var line in input)
    {
        ProcessLine(line);
    }

    var xMax = Math.Max(xFinishes.Max(), xStarts.Max()) + 1;
    var yMax = Math.Max(yFinishes.Max(), yStarts.Max()) + 1;

    grid = new int[yMax, xMax];
    for (var x = 0; x < xMax; x++)
    {
        for (var y = 0; y < yMax; y++)
        {
            grid[y,x] = 0;
        }
    }
    //grid.Dump();
    var dc = new DumpContainer();
    //dc.Content = grid;
    //dc.Dump();

    for (var i = 0; i < directions.Count; i++)
    {
        //dc.UpdateContent(grid);
        //input[i].Dump();
        if (directions[i] == Direction.Diagonal)
        {
            // don't make squares
            // 45 degrees is important because you basically want each point on an y = mx + b, where m is 1
            // So we mainly just need to determine if we have a negative or positive slope and then  we just move from
            // one point to the other by one.

            // Oh, yeah. And rise over run would help get the slope.
            var slope = (yStarts[i] - yFinishes[i]) / (xStarts[i] - xFinishes[i]);
            var b = yStarts[i] - slope * xStarts[i];

            var lowerX = Math.Min(xStarts[i], xFinishes[i]);
            var upperX = Math.Max(xStarts[i], xFinishes[i]);

            for (var x = lowerX; x <= upperX; x++)
            {
                //x.Dump();

                var y = slope * x + b;
                //y.Dump();
                //b.Dump();
                grid[y, x]++;
                if (grid[y, x] >= 2)
                {
                    intersections.Add(new Tuple<int, int>(x, y));
                }
            }
        }
        else
        {
            var lowerX = Math.Min(xStarts[i], xFinishes[i]);
            var upperX = Math.Max(xStarts[i], xFinishes[i]);

            var lowerY = Math.Min(yStarts[i], yFinishes[i]);
            var upperY = Math.Max(yStarts[i], yFinishes[i]);

            for (var x = lowerX; x <= upperX; x++)
            {
                for (var y = lowerY; y <= upperY; y++)
                {
                    //x.Dump();
                    //y.Dump();
                    grid[y, x]++;
                    if (grid[y, x] >= 2)
                    {
                        intersections.Add(new Tuple<int, int>(x, y));
                    }
                }
            }
        }
    }

    //grid.Dump();

    intersections.Distinct().Count().Dump();
    // 954973 not right
}

// Define other methods and classes here
void ProcessLine(string line)
{
    var parts = line.Split(new char[]{ ' ', ',', '-', '>' }, StringSplitOptions.RemoveEmptyEntries).Select(x => int.Parse(x)).ToArray();
    var x1 = parts[0];
    var y1 = parts[1];
    var x2 = parts[2];
    var y2 = parts[3];

    var direction = Direction.Diagonal;

    if (x1 == x2)
    {
        direction = Direction.Horizontal;
    }
    if (y1 == y2)
    {
        direction = Direction.Vertical;
    }

    directions.Add(direction);
    xStarts.Add(x1);
    xFinishes.Add(x2);
    yStarts.Add(y1);
    yFinishes.Add(y2);
}

enum Direction
{
    Horizontal,
    Vertical,
    Diagonal
}