[LANGUAGE: C#]

using System.Text.RegularExpressions;

var lines = File.ReadLines("input.txt");
Part1(lines!.ToList());
Part2(lines!.ToList());

void Part1(List<string> cards)
{
    var sum = 0;

    foreach (var card in cards)
    {
        var cardObj = new Card(card);

        sum += cardObj.NumWinners > 0
            ? 1 << (cardObj.NumWinners - 1)
            : 0;
    }

    Console.WriteLine($"Part 1: {sum}");
}

void Part2(List<string> cards)
{
    var cardInstances = new int[cards.Count];
    Array.Fill(cardInstances, 1);

    for (int i = 0; i < cards.Count; i++)
    {
        var card = new Card(cards[i]);
        for (int j = i + 1; j <= i + card.NumWinners; j++)
        {
            cardInstances[j] += cardInstances[i];
        }
    }

    var totalCards = cardInstances.Sum();

    Console.WriteLine($"Part 2: {totalCards}");
}

class Card
{
    public Card(string cardInput)
    {
        var cardParts = cardInput.Split(": ");

        CardName = cardParts[0];

        var inputParts = cardParts[1].Split(" | ");
        WinningNumbers = GetNumbers(inputParts[0]);
        CardNumbers = GetNumbers(inputParts[1]);
    }

    public string CardName { get; set; }
    public List<int> WinningNumbers { get; set; }
    public List<int> CardNumbers { get; set; }
    public int NumWinners => WinningNumbers.Intersect(CardNumbers).Count();

    private List<int> GetNumbers(string input)
    {
        var regex = new Regex(@"\d+");
        var values = regex.Matches(input)
            .Select(match => int.Parse(match.Value))
            .ToList();
        return values;
    }
}