Added day 9 solution (#7)

* Added day 9 scaffolding

* Added part 1 README

* Solved part 1

* Solver part 2

* Normalized line-ending

* Remove my inputs from repo

* Remove puzzle text from README

* Move day 9 to solved solution folder

* Added Rider run files

.run/Day09 example.run.xml

@@ -0,0 +1,21 @@
+<component name="ProjectRunConfigurationManager">
+    <configuration default="false" name="Day09 example" type="DotNetProject" factoryName=".NET Project"
+                   folderName="Day09">
+        <option name="EXE_PATH" value="$PROJECT_DIR$/Day09 - Mirage Maintenance/bin/Debug/net8.0/Day09.exe"/>
+        <option name="PROGRAM_PARAMETERS" value="example.txt"/>
+        <option name="WORKING_DIRECTORY" value="$PROJECT_DIR$/Day09 - Mirage Maintenance/bin/Debug/net8.0"/>
+        <option name="PASS_PARENT_ENVS" value="1"/>
+        <option name="USE_EXTERNAL_CONSOLE" value="0"/>
+        <option name="USE_MONO" value="0"/>
+        <option name="RUNTIME_ARGUMENTS" value=""/>
+        <option name="PROJECT_PATH" value="$PROJECT_DIR$/Day09 - Mirage Maintenance/Day09.csproj"/>
+        <option name="PROJECT_EXE_PATH_TRACKING" value="1"/>
+        <option name="PROJECT_ARGUMENTS_TRACKING" value="1"/>
+        <option name="PROJECT_WORKING_DIRECTORY_TRACKING" value="1"/>
+        <option name="PROJECT_KIND" value="DotNetCore"/>
+        <option name="PROJECT_TFM" value="net8.0"/>
+        <method v="2">
+            <option name="Build"/>
+        </method>
+    </configuration>
+</component>

.run/Day09.run.xml

@@ -0,0 +1,20 @@
+<component name="ProjectRunConfigurationManager">
+    <configuration default="false" name="Day09" type="DotNetProject" factoryName=".NET Project" folderName="Day09">
+        <option name="EXE_PATH" value="$PROJECT_DIR$/Day09 - Mirage Maintenance/bin/Debug/net8.0/Day09.exe"/>
+        <option name="PROGRAM_PARAMETERS" value=""/>
+        <option name="WORKING_DIRECTORY" value="$PROJECT_DIR$/Day09 - Mirage Maintenance/bin/Debug/net8.0"/>
+        <option name="PASS_PARENT_ENVS" value="1"/>
+        <option name="USE_EXTERNAL_CONSOLE" value="0"/>
+        <option name="USE_MONO" value="0"/>
+        <option name="RUNTIME_ARGUMENTS" value=""/>
+        <option name="PROJECT_PATH" value="$PROJECT_DIR$/Day09 - Mirage Maintenance/Day09.csproj"/>
+        <option name="PROJECT_EXE_PATH_TRACKING" value="1"/>
+        <option name="PROJECT_ARGUMENTS_TRACKING" value="1"/>
+        <option name="PROJECT_WORKING_DIRECTORY_TRACKING" value="1"/>
+        <option name="PROJECT_KIND" value="DotNetCore"/>
+        <option name="PROJECT_TFM" value="net8.0"/>
+        <method v="2">
+            <option name="Build"/>
+        </method>
+    </configuration>
+</component>

AdventOfCode2023.sln

@@ -34,6 +34,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Day07", "Day07 - Camel Card
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Day08", "Day08 - Haunted Wasteland\Day08.csproj", "{78787B01-0E1E-472E-8B58-4FFD864FC1F6}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Day09", "Day09 - Mirage Maintenance\Day09.csproj", "{1E0917F9-35B3-4474-B335-E72C6BDFE667}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -79,6 +81,10 @@ Global
 		{78787B01-0E1E-472E-8B58-4FFD864FC1F6}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{78787B01-0E1E-472E-8B58-4FFD864FC1F6}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{78787B01-0E1E-472E-8B58-4FFD864FC1F6}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1E0917F9-35B3-4474-B335-E72C6BDFE667}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1E0917F9-35B3-4474-B335-E72C6BDFE667}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1E0917F9-35B3-4474-B335-E72C6BDFE667}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1E0917F9-35B3-4474-B335-E72C6BDFE667}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{CE8086B8-A3E4-40E0-859F-607F95D25514} = {F6C05A63-6269-425F-B877-9E9F0BC1FC26}
@@ -89,5 +95,6 @@ Global
 		{6BA7E3DC-B970-457B-84FA-50034501273B} = {F6C05A63-6269-425F-B877-9E9F0BC1FC26}
 		{0A495922-31C5-4E5D-84AB-95262108E1D9} = {F6C05A63-6269-425F-B877-9E9F0BC1FC26}
 		{78787B01-0E1E-472E-8B58-4FFD864FC1F6} = {F6C05A63-6269-425F-B877-9E9F0BC1FC26}
+		{1E0917F9-35B3-4474-B335-E72C6BDFE667} = {F6C05A63-6269-425F-B877-9E9F0BC1FC26}
 	EndGlobalSection
 EndGlobal

Day09 - Mirage Maintenance/.vscode/launch.json

@@ -0,0 +1,18 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Launch (my input)",
+      "type": "coreclr",
+      "request": "launch",
+      "preLaunchTask": "build",
+      "program": "${workspaceFolder}/bin/Debug/net8.0/Day09.dll",
+      "args": [
+        "input.txt"
+      ],
+      "cwd": "${workspaceFolder}",
+      "console": "internalConsole",
+      "stopAtEntry": false
+    }
+  ]
+}

Day09 - Mirage Maintenance/.vscode/tasks.json

@@ -0,0 +1,21 @@
+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "label": "build",
+      "command": "dotnet",
+      "type": "process",
+      "group": {
+        "kind": "build",
+        "isDefault": true
+      },
+      "args": [
+        "build",
+        "${workspaceFolder}/Day09.csproj",
+        "/property:GenerateFullPaths=true",
+        "/consoleloggerparameters:NoSummary"
+      ],
+      "problemMatcher": "$msCompile"
+    }
+  ]
+}

Day09 - Mirage Maintenance/Day09.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>AdventOfCode.Year2023.Day09</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="mMosiur.AdventOfCode.Abstractions" Version="4.4.0" />
+    <PackageReference Include="mMosiur.AdventOfCode.Common" Version="0.1.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <None Update="*.txt">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
+
+</Project>

Day09 - Mirage Maintenance/Day09Solver.cs

@@ -0,0 +1,52 @@
+using AdventOfCode.Abstractions;
+using AdventOfCode.Year2023.Day09.Puzzle.Oasis;
+
+namespace AdventOfCode.Year2023.Day09;
+
+public sealed class Day09Solver : DaySolver
+{
+	public override int Year => 2023;
+	public override int Day => 9;
+	public override string Title => "Mirage Maintenance";
+
+	private readonly ReportReader _reportReader;
+	private Report? _report;
+
+	public Day09Solver(Day09SolverOptions options) : base(options)
+	{
+		_reportReader = new();
+	}
+
+	public Day09Solver(Action<Day09SolverOptions> configure)
+		: this(DaySolverOptions.FromConfigureAction(configure))
+	{
+	}
+
+	public Day09Solver() : this(new Day09SolverOptions())
+	{
+	}
+
+	public override string SolvePart1()
+	{
+		_report ??= _reportReader.ReadReport(InputLines);
+
+		int result = _report
+			.Histories
+			.Select(h => h.PredictNextValue())
+			.Sum();
+
+		return result.ToString();
+	}
+
+	public override string SolvePart2()
+	{
+		_report ??= _reportReader.ReadReport(InputLines);
+
+		int result = _report
+			.Histories
+			.Select(h => h.ExtrapolatePreviousValue())
+			.Sum();
+
+		return result.ToString();
+	}
+}

Day09 - Mirage Maintenance/Day09SolverOptions.cs

@@ -0,0 +1,7 @@
+using AdventOfCode.Abstractions;
+
+namespace AdventOfCode.Year2023.Day09;
+
+public sealed class Day09SolverOptions : DaySolverOptions
+{
+}

Day09 - Mirage Maintenance/Program.cs

@@ -0,0 +1,45 @@
+using System.Diagnostics;
+using AdventOfCode;
+using AdventOfCode.Year2023.Day09;
+
+try
+{
+	string? filepath = args.Length switch
+	{
+		0 => null,
+		1 => args[0],
+		_ => throw new CommandLineException(
+			$"Program was called with too many arguments. Proper usage: \"dotnet run [<input filepath>]\"."
+		)
+	};
+
+	Day09Solver solver = new(options =>
+	{
+		options.InputFilepath = filepath ?? options.InputFilepath;
+	});
+
+	Console.WriteLine($"--- Day {solver.Day}: {solver.Title} ---");
+
+	Console.Write("Part one: ");
+	string part1 = solver.SolvePart1();
+	Console.WriteLine(part1);
+
+	Console.Write("Part two: ");
+	string part2 = solver.SolvePart2();
+	Console.WriteLine(part2);
+}
+catch (AdventOfCodeException e)
+{
+	string errorPrefix = e switch
+	{
+		CommandLineException => "Command line error",
+		InputException => "Input error",
+		DaySolverException => "Day solver error",
+		_ => throw new UnreachableException($"Unknown exception type \"{e.GetType()}\".")
+	};
+
+	Console.ForegroundColor = ConsoleColor.Red;
+	Console.Error.WriteLine($"{errorPrefix}: {e.Message}");
+	Console.ResetColor();
+	Environment.Exit(1);
+}

Day09 - Mirage Maintenance/Puzzle/Oasis/Report.cs

@@ -0,0 +1,8 @@
+namespace AdventOfCode.Year2023.Day09.Puzzle.Oasis;
+
+internal sealed class Report(IEnumerable<ValueHistory> valueHistories)
+{
+	private readonly List<ValueHistory> _histories = valueHistories.ToList();
+
+	public IReadOnlyList<ValueHistory> Histories => _histories;
+}

Day09 - Mirage Maintenance/Puzzle/Oasis/ReportReader.cs

@@ -0,0 +1,30 @@
+using AdventOfCode.Common.SpanExtensions;
+
+namespace AdventOfCode.Year2023.Day09.Puzzle.Oasis;
+
+internal sealed class ReportReader
+{
+	public Report ReadReport(IEnumerable<string> inputLines)
+	{
+		var valueHistories = inputLines.Select(l => ReadReportLine(l));
+		return new Report(valueHistories);
+	}
+
+	private static ValueHistory ReadReportLine(ReadOnlySpan<char> line)
+	{
+		line = line.Trim();
+		int valueCount = line.Count(' ') + 1;
+		var values = new List<int>(valueCount);
+		foreach (var numberSpan in line.Split(' '))
+		{
+			if (!int.TryParse(numberSpan, out int number))
+			{
+				throw new InputException($"Invalid number format '{numberSpan}'.");
+			}
+
+			values.Add(number);
+		}
+
+		return new ValueHistory(values);
+	}
+}

Day09 - Mirage Maintenance/Puzzle/Oasis/ValueHistory.cs

@@ -0,0 +1,91 @@
+using System.Collections;
+
+namespace AdventOfCode.Year2023.Day09.Puzzle.Oasis;
+
+internal sealed class ValueHistory(IEnumerable<int> values)
+	: IReadOnlyList<int>
+{
+	private readonly int[] _valueHistory = values.ToArray();
+	private int? _previousValue;
+	private int? _nextValue;
+
+	public int Count => _valueHistory.Length;
+
+	public int this[int index] => _valueHistory[index];
+
+	public IEnumerator<int> GetEnumerator() => _valueHistory.AsEnumerable().GetEnumerator();
+	IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+	public int PredictNextValue()
+	{
+		_nextValue ??= InternalPredictNextValue();
+		return _nextValue.Value;
+	}
+
+	public int ExtrapolatePreviousValue()
+	{
+		_previousValue ??= InternalExtrapolatePreviousValue();
+		return _previousValue.Value;
+	}
+
+	private int InternalPredictNextValue()
+	{
+		Span<int> span = stackalloc int[Count];
+		_valueHistory.CopyTo(span);
+
+		int end = Count;
+
+		while (true)
+		{
+			end--;
+			int anyValueNonZero = 0;
+			for (int i = 0; i < end; i++)
+			{
+				int diff = span[i + 1] - span[i];
+				anyValueNonZero |= diff;
+				span[i] = diff;
+			}
+
+			if (anyValueNonZero == 0) break;
+		}
+
+		while (end < Count)
+		{
+			span[end] += span[end - 1];
+			end++;
+		}
+
+		return span[^1];
+	}
+
+	private int InternalExtrapolatePreviousValue()
+	{
+		Span<int> span = stackalloc int[Count];
+		_valueHistory.CopyTo(span);
+
+		int start = -1;
+
+		while (true)
+		{
+			start++;
+			int anyValueNonZero = 0;
+			for (int i = span.Length - 1; i > start; i--)
+			{
+				int diff = span[i] - span[i - 1];
+				anyValueNonZero |= diff;
+				span[i] = diff;
+			}
+
+			if (anyValueNonZero == 0) break;
+		}
+
+		while (start >= 0)
+		{
+			span[start] -= span[start + 1];
+			start--;
+		}
+
+
+		return span[0];
+	}
+}

Day09 - Mirage Maintenance/README.md

@@ -0,0 +1,5 @@
+# [Day 9: Mirage Maintenance](https://adventofcode.com/2023/day/9)
+
+You analyze environmental data from an oasis using the Oasis And Sand Instability Sensor (OASIS).
+The sensor provides a report of values and their changes over time.
+You're tasked with predicting the next value in each history by analyzing the differences between consecutive values and extrapolating.