Day 3 solution for part 1

AdventOfCode23.sln

@@ -7,6 +7,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Day1", "Day1\Day1.csproj",
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Day2", "Day2\Day2.csproj", "{1FB701F9-05FA-4D1D-97E5-9355C683E3D0}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Day3", "Day3\Day3.csproj", "{62336B74-EB88-4F21-9EBA-6FC5499155A2}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -24,5 +26,9 @@ Global
 		{1FB701F9-05FA-4D1D-97E5-9355C683E3D0}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{1FB701F9-05FA-4D1D-97E5-9355C683E3D0}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{1FB701F9-05FA-4D1D-97E5-9355C683E3D0}.Release|Any CPU.Build.0 = Release|Any CPU
+		{62336B74-EB88-4F21-9EBA-6FC5499155A2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{62336B74-EB88-4F21-9EBA-6FC5499155A2}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{62336B74-EB88-4F21-9EBA-6FC5499155A2}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{62336B74-EB88-4F21-9EBA-6FC5499155A2}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

Day3/Day3.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <RootNamespace>Day2</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Update="inputs\lan-input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="inputs\sample-input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="inputs\sample-input2.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="inputs\lar-input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
+
+</Project>

Day3/NumberToken.cs

@@ -0,0 +1,16 @@
+using System.Text.RegularExpressions;
+
+namespace Day3;
+
+public class NumberToken : Token
+{
+    public int Length { get; }
+    public int Value { get; }
+    
+    public NumberToken(int col, int row, string value)
+        : base(new Point2D(col, row))
+    {
+        Length = value.Length;
+        Value = int.Parse(value);
+    }
+}

Day3/Program.cs

@@ -0,0 +1,69 @@
+using Day3;
+
+if (args.Length < 1)
+{
+    Console.WriteLine("Requires 1 args: inputFileName");
+    return -1;
+}
+
+var inputFile = args[0];
+var parser = new SchematicParser();
+
+var set = new HashSet<Point2D>();
+var tokens = parser.Parse(inputFile).ToList();
+foreach (var token in tokens)
+{
+    if (token is SymbolToken sym)
+    {
+        foreach (var p in sym.Position.SurroundingAndSelf())
+        {
+            set.Add(p);
+        }
+    }
+}
+
+Console.WriteLine();
+
+for (var y = 0; y < parser.Height; y++)
+{
+    for (var x = 0; x < parser.Width; x++)
+    {
+        if (set.Contains(new Point2D(x, y)))
+        {
+            Console.Write("X");
+        }
+        else
+        {
+            Console.Write("-");
+        }
+    }
+    Console.WriteLine("|");
+}
+
+var sum = 0;
+foreach (var token in tokens)
+{
+    if (token is NumberToken num)
+    {
+        sum += IsTouchingSymbol(set, num);
+    }
+}
+
+Console.WriteLine();
+Console.WriteLine($"Sum: {sum}");
+
+return 0;
+
+int IsTouchingSymbol(ISet<Point2D> set, NumberToken num)
+{
+    for (var w = 0; w < num.Length; w++)
+    {
+        var p = num.Position with { X = num.Position.X + w };
+        if (set.Contains(p))
+        {
+            return num.Value;
+        }
+    }
+
+    return 0;
+}

Day3/SchematicParser.cs

@@ -0,0 +1,46 @@
+using System.Text.RegularExpressions;
+
+namespace Day3;
+
+public partial class SchematicParser
+{
+    [GeneratedRegex(@"\d+|[^\d.]+")]
+    private partial Regex TokenExtractor();
+    
+    public int Width { get; private set; }
+    public int Height { get; private set; }
+    
+    public IEnumerable<Token> Parse(string inputFile)
+    {
+        using var reader = File.OpenText(inputFile);
+        var row = 0;
+        while (!reader.EndOfStream)
+        {
+            var line = reader.ReadLine()!;
+            if (Width == 0)
+            {
+                Width = line.Length;
+            }
+            foreach (Match match in TokenExtractor().Matches(line))
+            {
+                if (match.Value[0] >= '0' && match.Value[0] <= '9')
+                {
+                    yield return new NumberToken(match.Index, row, match.Value);
+                }
+                else
+                {
+                    if (match.Length > 1)
+                    {
+                        throw new Exception($"Unexpected symbol token: {match.Value}");
+                    }
+
+                    yield return new SymbolToken(match.Index, row, match.Value);
+                }
+            }
+
+            row++;
+        }
+
+        Height = row;
+    }
+}

Day3/SymbolToken.cs

@@ -0,0 +1,12 @@
+namespace Day3;
+
+public class SymbolToken : Token
+{
+    public string Symbol { get; }
+    
+    public SymbolToken(int col, int row, string symbol)
+        : base(new Point2D(col, row))
+    {
+        Symbol = symbol;
+    }
+}

Day3/Token.cs

@@ -0,0 +1,25 @@
+namespace Day3;
+
+public record Point2D(int X, int Y)
+{
+    public IEnumerable<Point2D> SurroundingAndSelf()
+    {
+        for (var y = -1; y < 2; y++)
+        {
+            for (var x = -1; x < 2; x++)
+            {
+                yield return new Point2D(X + x, Y + y);
+            }
+        }
+    }
+}
+
+public abstract class Token
+{
+    public Point2D Position { get; }
+
+    protected Token(Point2D position)
+    {
+        Position = position;
+    }
+}

Day3/inputs/input-lar.txt

@@ -0,0 +1,140 @@
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+....................571.......................720..........269...........885.............................902...........80...738..........975

Day3/inputs/sample1.txt

@@ -0,0 +1,10 @@
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..