feat: solved day 3

03/MullItOver/Instruction.cs

@@ -0,0 +1,12 @@
+namespace MullItOver;
+
+public abstract class Instruction {};
+
+class MulInstruction(int multiplicandOne, int multiplicandTwo) : Instruction
+{
+  public int Execute() => multiplicandOne * multiplicandTwo;
+}
+
+class DontInstruction : Instruction;
+
+class DoInstruction : Instruction;

03/MullItOver/InstructionExtensions.cs

@@ -0,0 +1,28 @@
+namespace MullItOver;
+
+public static class InstructionExtensions
+{
+  public static int Execute(this List<Instruction> instructions)
+  {
+    var isEnabled = true;
+    var sum = 0;
+
+    foreach (var instruction in instructions)
+    {
+      switch (instruction)
+      {
+        case DontInstruction:
+          isEnabled = false;
+          continue;
+        case DoInstruction:
+          isEnabled = true;
+          continue;
+        case MulInstruction mul when isEnabled:
+          sum += mul.Execute();
+          continue;
+      }
+    }
+    
+    return sum;
+  }
+}

03/MullItOver/Program.cs

@@ -1,5 +1,7 @@
 using System.Diagnostics;
 
+using MullItOver;
+
 if (args.Length is 0)
 {
   Console.WriteLine("Please provide a path to the input file.");
@@ -18,21 +20,13 @@ var input = await File.ReadAllTextAsync(args[0]);
 var stopwatch = new Stopwatch();
 stopwatch.Start();
 
-var instructions = new PuzzleParser().Parse(input);
+var parser = new PuzzleParser();
 
-var results = 0;
+var instructions = isPart2 
+  ? parser.ParseWithConditionals(input)
+  : parser.Parse(input);
+
+var results = instructions.Execute();
 
 stopwatch.Stop();
-Console.WriteLine($"The sum of instructions is {results}. ({stopwatch.ElapsedMilliseconds}ms)");
-
-class PuzzleParser
-{
-  public List<Instruction> Parse(string input)
-  {
-    return [];
-  }
-}
-
-class Instruction(int multiplicandOne, int multiplicandTwo)
-{
-}
+Console.WriteLine($"The sum of instructions is {results}. ({stopwatch.ElapsedMilliseconds}ms)");

03/MullItOver/PuzzleParser.cs

@@ -0,0 +1,55 @@
+using System.Text.RegularExpressions;
+
+namespace MullItOver;
+
+partial class PuzzleParser
+{
+  [GeneratedRegex(@"mul\((\d{1,3}),(\d{1,3})\)")]
+  private static partial Regex InstructionsRegex();
+  
+  [GeneratedRegex(@"mul\((\d{1,3}),(\d{1,3})\)|do\(\)|don't\(\)")]
+  private static partial Regex InstructionsWithConditionalsRegex();
+  
+  public List<Instruction> Parse(string input)
+  {
+    var matches = InstructionsRegex().Matches(input);
+    return matches
+      .Select(Instruction (m) => new MulInstruction(
+        int.Parse(m.Groups[1].Value), 
+        int.Parse(m.Groups[2].Value)
+      ))
+      .ToList();
+  }
+  
+  public List<Instruction> ParseWithConditionals(string input)
+  {
+    var instructions = new List<Instruction>();
+    var matches = InstructionsWithConditionalsRegex()
+      .Matches(input)
+      .ToList();
+
+    foreach (var match in matches)
+    {
+      var firstGroup = match.Groups[0].Value;
+      
+      if (firstGroup.Contains("mul"))
+      {
+        instructions.Add(new MulInstruction(
+          int.Parse(match.Groups[1].Value), 
+          int.Parse(match.Groups[2].Value)
+        ));
+        continue;
+      }
+
+      if (firstGroup.Contains('\''))
+      {
+        instructions.Add(new DontInstruction());
+        continue;
+      }
+      
+      instructions.Add(new DoInstruction());
+    }
+
+    return instructions;
+  }
+}