#define Day13
#if Day13
using System.Text.RegularExpressions;

var text = File.ReadAllText("day13/input").Split("\n\n");
var points = text[0].Split("\n").Select(l => l.Split(","))
    .Select(p => new Point(int.Parse(p[0]), int.Parse(p[1]))).ToHashSet();

var reg = new Regex(@"fold along (?<c>x|y)=(?<p>\d+)");
var folds = reg.Matches(text[1]).Select(m => new Fold(m.Groups["c"].Value[0], int.Parse(m.Groups["p"].Value))).ToList();

foreach (var curFold in folds) {
    HashSet<Point> next = new HashSet<Point>();
    if (curFold.c == 'x') {
        foreach(var p in points) {
            if (p.x < curFold.p) {
                next.Add(p);
            } else if (p.x > curFold.p) {
                next.Add(new Point(curFold.p - (p.x - curFold.p), p.y));
            }
        }
    } else {
        foreach(var p in points) {
            if (p.y < curFold.p) {
                next.Add(p);
            } else if (p.y > curFold.p){
                next.Add(new Point(p.x, curFold.p - (p.y - curFold.p)));
            }
        }
    }
    points = next;
    Console.WriteLine(points.Count);
}

var maxX = points.Max(p => p.x);
var maxY = points.Max(p => p.y);

for (int y = 0; y <= maxY; y++) {
    for (int x = 0; x <= maxX; x++) {
        if (points.Contains(new Point(x, y))) {
            Console.Write("#");
        } else {
            Console.Write(".");
        }
    }
    Console.WriteLine();
}


record Point(int x, int y);
record Fold(char c, int p);
#endif