AdventofCode 2018 Day 03

int[,] canvas = null;

void Main()
{
    var aoc = new AdventOfCode(2018, 3);

    var input = new string[]{ "#1 @ 1,3: 4x4", "#2 @ 3,1: 4x4", "#3 @ 5,5: 2x2", }.Select(x=> new Paper(x)).ToArray();

    //test if all is working
    Debug.Assert(FillCanvas(10, input) == 4);
    Debug.Assert(FindSoloID(input) == 3);

    //get results
    input = aoc.InputLines.Select(x=> new Paper(x)).ToArray();

    //do your thing
    aoc.SubmitAnswer(FillCanvas(1000, input), Part.A);
    aoc.SubmitAnswer(FindSoloID(input), Part.B);



}
//class for each Paper part
class Paper
{
    public int ID;
    public int xStart;
    public int yStart;
    public int width;
    public int height;

    Regex regex = new Regex(@"#(\d+) @ (\d+),(\d+): (\d+)x(\d+)");
    public Paper(string line)
    {
        var match = regex.Match(line);

        this.ID = int.Parse(match.Groups[1].Value);
        this.xStart = int.Parse(match.Groups[2].Value);
        this.yStart = int.Parse(match.Groups[3].Value);
        this.width = int.Parse(match.Groups[4].Value);
        this.height = int.Parse(match.Groups[5].Value);

    }

}

int FillCanvas(int size, Paper[] papers)
{
    //create canvas
    canvas = new int[size,size];

    //check each paper
    foreach (var paper in papers)
    {
        //draw each paper
        for (int x = paper.xStart; x < paper.xStart + paper.width; x++)
        {
            for (int y = paper.yStart; y < paper.yStart + paper.height; y++)
            {
                //increment for how many papers are on this position
                canvas[x, y]++;
            }
        }
    }

    //flatten and count >= 2
    return canvas.Cast<int>().Where(x=> x >= 2).Count();
}


int FindSoloID(Paper[] papers)
{
    //check all papers
    foreach (var paper in papers)
    {
        for (int x = paper.xStart; x < paper.xStart + paper.width; x++)
        {
            for (int y = paper.yStart; y < paper.yStart + paper.height; y++)
            {
                //this paper has more than 1, so not it
                if (canvas[x, y] != 1) goto FAILED;

            }
        }

        //this one has all
        return paper.ID;
    FAILED:
        continue;
    }
    throw new ObjectNotFoundException();
}
// Define other methods and classes here