Finish Day 08

.vscode/launch.json

@@ -80,6 +80,17 @@
             "cwd": "${workspaceFolder}",
             "stopAtEntry": false,
             "console": "internalConsole"
+        },
+        {
+            "name": "aoc-2024-08 Debug",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "dotnet: build aoc-2024-08",
+            "program": "${workspaceFolder}/artifacts/bin/aoc-2024-08/debug/aoc-2024-08.dll",
+            "args": ["part-one", "data/2024/08/dev.txt"],
+            "cwd": "${workspaceFolder}",
+            "stopAtEntry": false,
+            "console": "internalConsole"
         }
     ]
 }

.vscode/tasks.json

@@ -58,6 +58,14 @@
             "group": "build",
             "problemMatcher": [],
             "label": "dotnet: build aoc-2024-07"
+        },
+        {
+            "type": "dotnet",
+            "task": "build aoc-2024-08.csproj",
+            "file": "src/2024/08/aoc-2024-08.csproj",
+            "group": "build",
+            "problemMatcher": [],
+            "label": "dotnet: build aoc-2024-08"
         }
     ]
 }

AdventOfCode.sln

@@ -1,4 +1,4 @@
-
+
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.0.31903.59
@@ -19,6 +19,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "aoc-2024-06", "src\2024\06\
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "aoc-2024-07", "src\2024\07\aoc-2024-07.csproj", "{58941BB2-E4AC-40F0-AA92-BEF51DEFC859}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "aoc-2024-08", "src\2024\08\aoc-2024-08.csproj", "{44BBC1CF-D2FC-4906-9691-B439EC9EFB8C}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "core", "src\core\core.csproj", "{9E2BD5D6-55DD-4760-AD30-75B168F03F60}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -56,6 +60,14 @@ Global
 		{58941BB2-E4AC-40F0-AA92-BEF51DEFC859}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{58941BB2-E4AC-40F0-AA92-BEF51DEFC859}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{58941BB2-E4AC-40F0-AA92-BEF51DEFC859}.Release|Any CPU.Build.0 = Release|Any CPU
+		{44BBC1CF-D2FC-4906-9691-B439EC9EFB8C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{44BBC1CF-D2FC-4906-9691-B439EC9EFB8C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{44BBC1CF-D2FC-4906-9691-B439EC9EFB8C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{44BBC1CF-D2FC-4906-9691-B439EC9EFB8C}.Release|Any CPU.Build.0 = Release|Any CPU
+		{9E2BD5D6-55DD-4760-AD30-75B168F03F60}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9E2BD5D6-55DD-4760-AD30-75B168F03F60}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9E2BD5D6-55DD-4760-AD30-75B168F03F60}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9E2BD5D6-55DD-4760-AD30-75B168F03F60}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{FAF70800-E2C3-4AD7-B433-86C1F20380F7} = {37CA8017-085A-4F6A-BADB-535F929C10B9}
@@ -65,5 +77,6 @@ Global
 		{D108A6AB-B974-4BD9-B97A-CB1D1A2F3920} = {37CA8017-085A-4F6A-BADB-535F929C10B9}
 		{EEC6EF36-EE16-4DB4-9AE8-CF0234751458} = {37CA8017-085A-4F6A-BADB-535F929C10B9}
 		{58941BB2-E4AC-40F0-AA92-BEF51DEFC859} = {37CA8017-085A-4F6A-BADB-535F929C10B9}
+		{44BBC1CF-D2FC-4906-9691-B439EC9EFB8C} = {37CA8017-085A-4F6A-BADB-535F929C10B9}
 	EndGlobalSection
 EndGlobal

src/2024/08/Program.cs

@@ -0,0 +1,58 @@
+using System.Collections.Immutable;
+
+using ConsoleAppFramework;
+
+using core;
+
+var builder = ConsoleApp.Create();
+builder.Add("part-one", static ([Argument, FileExists] string file) =>
+{
+	Console.WriteLine($"Result: {ReadFile(file, false)}");
+});
+builder.Add("part-two", static ([Argument, FileExists] string file) =>
+{
+	Console.WriteLine($"Result: {ReadFile(file, true)}");
+});
+builder.Run(args);
+
+static int ReadFile(string path, bool resonant)
+{
+	SymbolGrid grid = new();
+	grid.Load(path);
+	ScenarioMap map = new(grid);
+	HashSet<Vector2I> antinodes = [];
+	foreach (var (key, set) in map.Antennas)
+	{
+		for (int l = set.Length - 1; l > 0; l--)
+		{
+			for (int r = 0; r < l; r++)
+			{
+				var d = set[l] - set[r];
+				for (int i = resonant ? 1 : 2; resonant || i < 3; i++)
+				{
+					bool valid = false;
+					var fl = set[l] - d * i;
+					if (grid.IsValid(fl))
+					{
+						valid = true;
+						antinodes.Add(fl);
+					}
+
+					var fr = set[r] + d * i;
+					if (grid.IsValid(fr))
+					{
+						valid = true;
+						antinodes.Add(fr);
+					}
+
+					if (!valid)
+					{
+						break;
+					}
+				}
+			}
+		}
+	}
+
+	return antinodes.Count;
+}

src/2024/08/ScenarioMap.cs

@@ -0,0 +1,31 @@
+using System.Collections.Frozen;
+using System.Collections.Immutable;
+using System.Runtime.InteropServices;
+
+using core;
+
+record class ScenarioMap
+{
+	private readonly SymbolGrid _grid;
+
+	public FrozenDictionary<char, ImmutableArray<Vector2I>> Antennas { get; }
+
+	public ScenarioMap(SymbolGrid grid)
+	{
+		_grid = grid;
+		Dictionary<char, HashSet<Vector2I>> antennas = [];
+		foreach (var (position, symbol) in grid)
+		{
+			if (char.IsLetterOrDigit(symbol))
+			{
+				(CollectionsMarshal.GetValueRefOrAddDefault(
+					antennas,
+					symbol,
+					out _
+				) ??= []).Add(position);
+			}
+		}
+
+		Antennas = antennas.ToFrozenDictionary(c => c.Key, c => (ImmutableArray<Vector2I>)[.. c.Value]);
+	}
+}

src/2024/08/aoc-2024-08.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\core\core.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <RootNamespace>aoc_2024_08</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

src/core/FileExistsAttribute.cs

@@ -0,0 +1,8 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace core;
+
+public class FileExistsAttribute : ValidationAttribute
+{
+	public override bool IsValid(object? value) => value is string path && File.Exists(path);
+}

src/core/SymbolGrid.cs

@@ -0,0 +1,126 @@
+using System.Diagnostics.CodeAnalysis;
+using System.IO.MemoryMappedFiles;
+using System.Numerics;
+
+namespace core;
+
+public class SymbolGrid
+{
+	private char[]? _map;
+
+	[DisallowNull]
+	public char? this[int x, int y]
+	{
+		get
+		{
+			EnsureMap();
+			return IsValid(x, y) ? _map[y * Height + x] : null;
+		}
+		set
+		{
+			EnsureMap();
+			if (IsValid(x, y))
+			{
+				_map[y * Height + x] = value.Value;
+			}
+		}
+	}
+
+	[DisallowNull]
+	public char? this[Vector2I i]
+	{
+		get => this[i.X, i.Y];
+		set => this[i.X, i.Y] = value;
+	}
+
+	public int Width { get; private set; }
+
+	public int Height { get; private set; }
+
+	public void Load(string file)
+	{
+		using var fileView = MemoryMappedFile.CreateFromFile(file, FileMode.Open);
+		using var accessor = fileView.CreateViewAccessor();
+		(Width, var stride, Height) = Parse(accessor);
+		_map = new char[Width * Height];
+		for (int x = 0; x < Width; x++)
+		{
+			for (int y = 0; y < Height; y++)
+			{
+				_map[y * Height + x] = (char)accessor.ReadByte(y * stride + x);
+			}
+		}
+
+		static (int Width, int Stride, int Height) Parse(MemoryMappedViewAccessor map)
+		{
+			bool hasNewLine = false;
+			int? width = null, stride = null;
+			for (int i = 0; i < map.Capacity; i++)
+			{
+				if ((char)map.ReadByte(i) is '\r' or '\n')
+				{
+					if (!hasNewLine)
+					{
+						width = i;
+					}
+
+					hasNewLine = true;
+				}
+				else if (hasNewLine)
+				{
+					stride = i;
+					break;
+				}
+			}
+
+			return (width!.Value, stride!.Value, (int)((map.Capacity + width.Value) / stride.Value));
+		}
+	}
+
+	public SymbolEnumerator GetEnumerator() => new(this);
+
+	public bool IsValid(Vector2I p) => IsValid(p.X, p.Y);
+
+	public bool IsValid(int x, int y)
+	{
+		EnsureMap();
+		return x >= 0 && x < Width && y >= 0 && y < Height;
+	}
+
+	public ref struct SymbolEnumerator
+	{
+		private readonly SymbolGrid _grid;
+		private readonly int _length;
+		private int? _current;
+
+		internal SymbolEnumerator(SymbolGrid grid)
+		{
+			_grid = grid;
+			_length = grid.Width * grid.Height;
+		}
+
+		public (Vector2I Position, char Symbol) Current { get; private set; }
+
+		public bool MoveNext()
+		{
+			_current = _current.HasValue ? _current + 1 : 0;
+			if (_current == _length)
+			{
+				return false;
+			}
+
+			Current = (_grid.ToVector(_current.Value), _grid._map![_current.Value]);
+
+			return true;
+		}
+	}
+
+	private Vector2I ToVector(int index) => new()
+	{
+		Y = index / Height,
+		X = index % Height
+	};
+
+	[MemberNotNull(nameof(_map))]
+	private void EnsureMap() => ArgumentNullException.ThrowIfNull(_map);
+}

src/core/Vector2I.cs

@@ -0,0 +1,28 @@
+using System.Numerics;
+
+namespace core;
+
+public record struct Vector2I(int X, int Y) :
+IAdditionOperators<Vector2I, Vector2I, Vector2I>,
+ISubtractionOperators<Vector2I, Vector2I, Vector2I>,
+IMultiplyOperators<Vector2I, int, Vector2I>
+{
+	public readonly double Length => Math.ReciprocalSqrtEstimate(SquareLength);
+
+	public readonly int SquareLength => X * X + Y * Y;
+
+	public static Vector2I operator +(Vector2I left, Vector2I right)
+	{
+		return new(left.X + right.X, left.Y + right.Y);
+	}
+
+	public static Vector2I operator -(Vector2I left, Vector2I right)
+	{
+		return new(left.X - right.X, left.Y - right.Y);
+	}
+
+	public static Vector2I operator *(Vector2I left, int right)
+	{
+		return new(left.X * right, left.Y * right);
+	}
+}

src/core/core.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>