[2023] Finish Day4

- Yes, did skip day 3 💀

Signed-off-by: TiagoRG <tiago.rgarcia@ua.pt>

Year2023/Day4.cs

@@ -0,0 +1,67 @@
+using System.Text.RegularExpressions;
+
+namespace AdventOfCode.Year2023;
+
+public static class Day4
+{
+    private class Card
+    {
+        public int CardNumber { get; set; }
+        public int[]? WinningNumbers { get; set; }
+        public int[]? Numbers { get; set; }
+        public int ValidNumbers { get; set; }
+    }
+
+    private static List<Card> Cards = new();
+    private static double Sum;
+
+    public static void Run()
+    {
+        File.ReadAllLines("inputs/Year2023/day4.txt").ToList().ForEach(line =>
+        {
+            Card card = new Card();
+            card.CardNumber = Convert.ToInt32(Regex.Split(line.Split(": ")[0], @"\s+").Last());
+            string[] cardNumbers = Regex.Split(line.Split(": ")[1], @"\s+\|\s+");
+            card.WinningNumbers = Regex.Split(cardNumbers.First(), @"\W+").Where(x => !string.IsNullOrEmpty(x)).Select(x => Convert.ToInt32(x)).ToArray();
+            card.Numbers = Regex.Split(cardNumbers.Last(), @"\W+").Where(x => !string.IsNullOrEmpty(x)).Select(x => Convert.ToInt32(x)).ToArray();
+            Cards.Add(card);
+        });
+
+        Cards.ForEach(card =>
+        {
+            card.ValidNumbers = 0;
+            card.Numbers!.ToList().ForEach(number => card.ValidNumbers += card.WinningNumbers!.Contains(number) ? 1 : 0);
+        });
+
+        Console.WriteLine($@"
+Day4 Solution
+Part1 Result: {Part1()}
+Part2 Result: {Part2()}
+
+=============================");
+    }
+
+    private static double Part1()
+    {
+        Sum = 0;
+        Cards.ForEach(card => Sum += card.ValidNumbers > 0 ? Math.Pow(2, card.ValidNumbers - 1) : 0);
+        return Sum;
+    }
+
+    private static double Part2()
+    {
+        Sum = 0;
+
+        Dictionary<int, int> CardInstances = new();
+        Cards.ForEach(card => CardInstances.Add(card.CardNumber, 1));
+        Cards.ForEach(card =>
+        {
+            for (int i = card.CardNumber + 1; i <= card.CardNumber + card.ValidNumbers; i++)
+                CardInstances[i] += CardInstances[card.CardNumber];
+
+            Sum += CardInstances[card.CardNumber];
+        });
+
+        return Sum;
+    }
+}

Year2023/Loader2023.cs

@@ -12,6 +12,7 @@ public static class Loader2023
 
         Day1.Run();
         Day2.Run();
+        Day4.Run();
     }
 }