Part 2

AdventOfCode/AdventOfCode.csproj

@@ -47,6 +47,7 @@
 	<None Remove="problems\aoc2023\day3\sample.txt" />
 	<None Remove="problems\aoc2023\day3\sara.txt" />
 	<None Remove="problems\aoc2023\day4\input.txt" />
+	<None Remove="problems\aoc2023\day4\sample.txt" />
   </ItemGroup>
 
 

AdventOfCode/Problems/AOC2023/Day4/Scratchcards.cs

@@ -11,6 +11,7 @@ namespace AdventOfCode.Problems.AOC2023.Day4;
 internal class Scratchcards : Problem<double, int>
 {
 	private (int card, int[] win, int[] have)[] _cards = [];
+	private Dictionary<int, int> _cardCount = new ();
 
 	public override void CalculatePart1()
 	{
@@ -22,7 +23,32 @@ internal class Scratchcards : Problem<double, int>
 
 	public override void CalculatePart2()
 	{
-		throw new NotImplementedException();
+		Part2 = _cards.Length;
+		for (int i = 0; i < _cards.Length; i++)
+		{
+			var card = _cards[i];
+			var wins = card.have.Intersect(card.win).Count();
+			for (int j = 1; j <= wins; j++)
+				AddCards(card.card + j, GetCardCount(card.card));
+			Part2 += wins * GetCardCount(card.card);
+			//_cardCount[card.card] = 0;
+		}
+	}
+
+	private int GetCardCount(int card)
+	{
+		if(_cardCount.TryGetValue(card, out var count)) 
+			return count;
+		//_cardCount.Add(card, 1);
+		return 1;
+	}
+
+	private void AddCards(int card, int count)
+	{
+		if(_cardCount.ContainsKey(card))
+			_cardCount[card] += count;
+		else
+			_cardCount.Add(card, count + 1);
 	}
 
 	public override void LoadInput()

AdventOfCode/Problems/AOC2023/Day4/sample.txt

@@ -0,0 +1,6 @@
+Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
+Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
+Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
+Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
+Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
+Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11