From d999774ec107dbce0f0f03c64a0d9d765cd9e818 Mon Sep 17 00:00:00 2001
From: TiagoRG <tiago.rgarcia@ua.pt>
Date: Mon, 4 Dec 2023 17:28:27 +0000
Subject: [PATCH] [2023] Finish Day4

- Yes, did skip day 3 :skull:

Signed-off-by: TiagoRG <tiago.rgarcia@ua.pt>
---
 Year2023/Day4.cs       | 67 ++++++++++++++++++++++++++++++++++++++++++
 Year2023/Loader2023.cs |  1 +
 2 files changed, 68 insertions(+)
 create mode 100644 Year2023/Day4.cs

diff --git a/Year2023/Day4.cs b/Year2023/Day4.cs
new file mode 100644
index 0000000..2a46647
--- /dev/null
+++ b/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;
+    }
+}
diff --git a/Year2023/Loader2023.cs b/Year2023/Loader2023.cs
index 899dbec..402d7c1 100644
--- a/Year2023/Loader2023.cs
+++ b/Year2023/Loader2023.cs
@@ -12,6 +12,7 @@ public static class Loader2023
 
         Day1.Run();
         Day2.Run();
+        Day4.Run();
     }
 }