feat: solve part 2

10/PipeMaze.Tests/GlobalUsings.cs

@@ -1,2 +1,3 @@
-global using Xunit;
 global using FluentAssertions;
+
+global using Xunit;

10/PipeMaze.Tests/MazeTests.cs

@@ -36,13 +36,25 @@ public class MazeTests
   [MemberData(nameof(TestData.FurthestStepFromStartTestData), MemberType = typeof(TestData))]
   public void FurthestStepFromStart_WhenGivenInput_ItShouldReturnExpectedFurthestStepFromStart(Maze maze, int expectedFurthestStepFromStart)
   {
-    maze.FarthestStepFromStart
+    maze.GetFarthestStepFromStart()
       .Should()
       .Be(expectedFurthestStepFromStart);
   }
 
+  [Theory]
+  [MemberData(nameof(TestData.AreaTestData), MemberType = typeof(TestData))]
+  public void Area_WhenGivenInput_ItShouldReturnExpectedArea(string[] input, int expectedArea)
+  {
+    var maze = Maze.Parse(input);
+    maze.GetAreaOfLoop()
+      .Should()
+      .Be(expectedArea);
+  }
+
   public static class TestData
   {
+    private static readonly string[] Input = File.ReadAllLines("INPUT.txt");
+
     private static readonly string[] TestMazeInput =
     {
       ".....",
@@ -68,6 +80,66 @@ public class MazeTests
         ]
       );
 
+    public static IEnumerable<object[]> AreaTestData =>
+      new List<object[]>
+      {
+        new object[]
+        {
+          new string[]
+          {
+            "...........",
+            ".S-------7.",
+            ".|F-----7|.",
+            ".||.....||.",
+            ".||.....||.",
+            ".|L-7.F-J|.",
+            ".|..|.|..|.",
+            ".L--J.L--J.",
+            "...........",
+          },
+          4,
+        },
+        new object[]
+        {
+          new string[]
+          {
+            ".F----7F7F7F7F-7....",
+            ".|F--7||||||||FJ....",
+            ".||.FJ||||||||L7....",
+            "FJL7L7LJLJ||LJ.L-7..",
+            "L--J.L7...LJS7F-7L7.",
+            "....F-J..F7FJ|L7L7L7",
+            "....L7.F7||L7|.L7L7|",
+            ".....|FJLJ|FJ|F7|.LJ",
+            "....FJL-7.||.||||...",
+            "....L---J.LJ.LJLJ...",
+          },
+          8
+        },
+        new object[]
+        {
+          new string[]
+          {
+            "FF7FSF7F7F7F7F7F---7",
+            "L|LJ||||||||||||F--J",
+            "FL-7LJLJ||||||LJL-77",
+            "F--JF--7||LJLJ7F7FJ-",
+            "L---JF-JLJ.||-FJLJJ7",
+            "|F|F-JF---7F7-L7L|7|",
+            "|FFJF7L7F-JF7|JL---7",
+            "7-L-JL7||F7|L7F-7F7|",
+            "L.L7LFJ|||||FJL7||LJ",
+            "L7JLJL-JLJLJL--JLJ.L",
+          },
+          10
+        },
+        new object[]
+        {
+          Input,
+          287,
+        }
+      };
+
     public static IEnumerable<object[]> FurthestStepFromStartTestData =>
       new List<object[]>
       {
@@ -112,6 +184,11 @@ public class MazeTests
             ]
           ),
           8,
+        },
+        new object[]
+        {
+          Maze.Parse(Input),
+          6870,
         }
       };
 

10/PipeMaze.Tests/PipeMaze.Tests.csproj

@@ -27,4 +27,10 @@
     <ProjectReference Include="..\PipeMaze\PipeMaze.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Content Include="..\INPUT.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
 </Project>

10/PipeMaze/Program.cs

@@ -1,4 +1,5 @@
 using System.Diagnostics;
+using System.Runtime.CompilerServices;
 
 namespace PipeMaze;
 
@@ -18,21 +19,31 @@ public class Program
       return -2;
     }
 
+    var isPart2 = args.Length > 1 && args[1] == "part2";
     var input = await File.ReadAllLinesAsync(args[0]);
 
     var stopwatch = new Stopwatch();
     stopwatch.Start();
 
-    var result = Maze.Parse(input).FarthestStepFromStart;
+    var maze = Maze.Parse(input);
+    var result = isPart2 ? maze.GetAreaOfLoop() : maze.GetFarthestStepFromStart();
 
     stopwatch.Stop();
 
-    Console.WriteLine($"The farthest step from the starting pipe is {result}. ({stopwatch.ElapsedMilliseconds}ms)");
+    if (isPart2)
+    {
+      Console.WriteLine($"The area of the loop is {result}. ({stopwatch.ElapsedMilliseconds}ms)");
+    }
+    else
+    {
+      Console.WriteLine($"The farthest step from the start is {result}. ({stopwatch.ElapsedMilliseconds}ms)");
+    }
 
     return result;
   }
 }
 
+
 public class Maze(
   int width,
   int height,
@@ -56,7 +67,43 @@ public class Maze(
 
   public Pipe? StartingPipe => Pipes.FirstOrDefault(p => p.Type is PipeType.Unknown);
 
-  public int FarthestStepFromStart => GetLoop().Count / 2;
+  public int GetFarthestStepFromStart() => GetLoop().Count / 2;
+
+  public int GetAreaOfLoop()
+  {
+    var count = 0;
+    var loop = GetLoop();
+    var areInsideLoop = false;
+    var verticalBoundaries = new List<PipeType>()
+    {
+      PipeType.UpAndDown,
+      PipeType.UpAndRight,
+      PipeType.UpAndLeft,
+    };
+
+    for (var row = 0; row < Height; row++)
+    {
+      for (var column = 0; column < Width; column++)
+      {
+        var pipe = loop.FirstOrDefault(p => p.Coordinate.Column == column && p.Coordinate.Row == row);
+
+        if (pipe is null && areInsideLoop is true)
+        {
+          count++;
+        }
+
+        if (
+          pipe is not null &&
+          verticalBoundaries.Contains(pipe.Type) is true
+        )
+        {
+          areInsideLoop = !areInsideLoop;
+        }
+      }
+    }
+
+    return count;
+  }
 
   public List<Pipe> GetLoop()
   {