namespace Day4; public class ScratchCard { public int Id { get; } public ISet Winning { get; } = new HashSet(); public ISet Draw { get; } = new HashSet(); public ScratchCard(int id) { Id = id; } public int GetMatches() { return Draw.Select(draw => Winning.Contains(draw) ? 1 : 0).Sum(); } public int GetScore() { var matches = GetMatches(); return matches > 0 ? (int)Math.Pow(2, matches - 1) : 0; } }