initial commit, day 10

dotnet/.gitignore

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+## Ignore Visual Studio temporary files, build results, and
+## files generated by popular Visual Studio add-ons.
+##
+## Get latest from `dotnet new gitignore`
+
+# dotenv files
+.env
+
+# User-specific files
+*.rsuser
+*.suo
+*.user
+*.userosscache
+*.sln.docstates
+
+# User-specific files (MonoDevelop/Xamarin Studio)
+*.userprefs
+
+# Mono auto generated files
+mono_crash.*
+
+# Build results
+[Dd]ebug/
+[Dd]ebugPublic/
+[Rr]elease/
+[Rr]eleases/
+x64/
+x86/
+[Ww][Ii][Nn]32/
+[Aa][Rr][Mm]/
+[Aa][Rr][Mm]64/
+bld/
+[Bb]in/
+[Oo]bj/
+[Ll]og/
+[Ll]ogs/
+
+# Visual Studio 2015/2017 cache/options directory
+.vs/
+# Uncomment if you have tasks that create the project's static files in wwwroot
+#wwwroot/
+
+# Visual Studio 2017 auto generated files
+Generated\ Files/
+
+# MSTest test Results
+[Tt]est[Rr]esult*/
+[Bb]uild[Ll]og.*
+
+# NUnit
+*.VisualState.xml
+TestResult.xml
+nunit-*.xml
+
+# Build Results of an ATL Project
+[Dd]ebugPS/
+[Rr]eleasePS/
+dlldata.c
+
+# Benchmark Results
+BenchmarkDotNet.Artifacts/
+
+# .NET
+project.lock.json
+project.fragment.lock.json
+artifacts/
+
+# Tye
+.tye/
+
+# ASP.NET Scaffolding
+ScaffoldingReadMe.txt
+
+# StyleCop
+StyleCopReport.xml
+
+# Files built by Visual Studio
+*_i.c
+*_p.c
+*_h.h
+*.ilk
+*.meta
+*.obj
+*.iobj
+*.pch
+*.pdb
+*.ipdb
+*.pgc
+*.pgd
+*.rsp
+*.sbr
+*.tlb
+*.tli
+*.tlh
+*.tmp
+*.tmp_proj
+*_wpftmp.csproj
+*.log
+*.tlog
+*.vspscc
+*.vssscc
+.builds
+*.pidb
+*.svclog
+*.scc
+
+# Chutzpah Test files
+_Chutzpah*
+
+# Visual C++ cache files
+ipch/
+*.aps
+*.ncb
+*.opendb
+*.opensdf
+*.sdf
+*.cachefile
+*.VC.db
+*.VC.VC.opendb
+
+# Visual Studio profiler
+*.psess
+*.vsp
+*.vspx
+*.sap
+
+# Visual Studio Trace Files
+*.e2e
+
+# TFS 2012 Local Workspace
+$tf/
+
+# Guidance Automation Toolkit
+*.gpState
+
+# ReSharper is a .NET coding add-in
+_ReSharper*/
+*.[Rr]e[Ss]harper
+*.DotSettings.user
+
+# TeamCity is a build add-in
+_TeamCity*
+
+# DotCover is a Code Coverage Tool
+*.dotCover
+
+# AxoCover is a Code Coverage Tool
+.axoCover/*
+!.axoCover/settings.json
+
+# Coverlet is a free, cross platform Code Coverage Tool
+coverage*.json
+coverage*.xml
+coverage*.info
+
+# Visual Studio code coverage results
+*.coverage
+*.coveragexml
+
+# NCrunch
+_NCrunch_*
+.*crunch*.local.xml
+nCrunchTemp_*
+
+# MightyMoose
+*.mm.*
+AutoTest.Net/
+
+# Web workbench (sass)
+.sass-cache/
+
+# Installshield output folder
+[Ee]xpress/
+
+# DocProject is a documentation generator add-in
+DocProject/buildhelp/
+DocProject/Help/*.HxT
+DocProject/Help/*.HxC
+DocProject/Help/*.hhc
+DocProject/Help/*.hhk
+DocProject/Help/*.hhp
+DocProject/Help/Html2
+DocProject/Help/html
+
+# Click-Once directory
+publish/
+
+# Publish Web Output
+*.[Pp]ublish.xml
+*.azurePubxml
+# Note: Comment the next line if you want to checkin your web deploy settings,
+# but database connection strings (with potential passwords) will be unencrypted
+*.pubxml
+*.publishproj
+
+# Microsoft Azure Web App publish settings. Comment the next line if you want to
+# checkin your Azure Web App publish settings, but sensitive information contained
+# in these scripts will be unencrypted
+PublishScripts/
+
+# NuGet Packages
+*.nupkg
+# NuGet Symbol Packages
+*.snupkg
+# The packages folder can be ignored because of Package Restore
+**/[Pp]ackages/*
+# except build/, which is used as an MSBuild target.
+!**/[Pp]ackages/build/
+# Uncomment if necessary however generally it will be regenerated when needed
+#!**/[Pp]ackages/repositories.config
+# NuGet v3's project.json files produces more ignorable files
+*.nuget.props
+*.nuget.targets
+
+# Microsoft Azure Build Output
+csx/
+*.build.csdef
+
+# Microsoft Azure Emulator
+ecf/
+rcf/
+
+# Windows Store app package directories and files
+AppPackages/
+BundleArtifacts/
+Package.StoreAssociation.xml
+_pkginfo.txt
+*.appx
+*.appxbundle
+*.appxupload
+
+# Visual Studio cache files
+# files ending in .cache can be ignored
+*.[Cc]ache
+# but keep track of directories ending in .cache
+!?*.[Cc]ache/
+
+# Others
+ClientBin/
+~$*
+*~
+*.dbmdl
+*.dbproj.schemaview
+*.jfm
+*.pfx
+*.publishsettings
+orleans.codegen.cs
+
+# Including strong name files can present a security risk
+# (https://github.com/github/gitignore/pull/2483#issue-259490424)
+#*.snk
+
+# Since there are multiple workflows, uncomment next line to ignore bower_components
+# (https://github.com/github/gitignore/pull/1529#issuecomment-104372622)
+#bower_components/
+
+# RIA/Silverlight projects
+Generated_Code/
+
+# Backup & report files from converting an old project file
+# to a newer Visual Studio version. Backup files are not needed,
+# because we have git ;-)
+_UpgradeReport_Files/
+Backup*/
+UpgradeLog*.XML
+UpgradeLog*.htm
+ServiceFabricBackup/
+*.rptproj.bak
+
+# SQL Server files
+*.mdf
+*.ldf
+*.ndf
+
+# Business Intelligence projects
+*.rdl.data
+*.bim.layout
+*.bim_*.settings
+*.rptproj.rsuser
+*- [Bb]ackup.rdl
+*- [Bb]ackup ([0-9]).rdl
+*- [Bb]ackup ([0-9][0-9]).rdl
+
+# Microsoft Fakes
+FakesAssemblies/
+
+# GhostDoc plugin setting file
+*.GhostDoc.xml
+
+# Node.js Tools for Visual Studio
+.ntvs_analysis.dat
+node_modules/
+
+# Visual Studio 6 build log
+*.plg
+
+# Visual Studio 6 workspace options file
+*.opt
+
+# Visual Studio 6 auto-generated workspace file (contains which files were open etc.)
+*.vbw
+
+# Visual Studio 6 auto-generated project file (contains which files were open etc.)
+*.vbp
+
+# Visual Studio 6 workspace and project file (working project files containing files to include in project)
+*.dsw
+*.dsp
+
+# Visual Studio 6 technical files
+*.ncb
+*.aps
+
+# Visual Studio LightSwitch build output
+**/*.HTMLClient/GeneratedArtifacts
+**/*.DesktopClient/GeneratedArtifacts
+**/*.DesktopClient/ModelManifest.xml
+**/*.Server/GeneratedArtifacts
+**/*.Server/ModelManifest.xml
+_Pvt_Extensions
+
+# Paket dependency manager
+.paket/paket.exe
+paket-files/
+
+# FAKE - F# Make
+.fake/
+
+# CodeRush personal settings
+.cr/personal
+
+# Python Tools for Visual Studio (PTVS)
+__pycache__/
+*.pyc
+
+# Cake - Uncomment if you are using it
+# tools/**
+# !tools/packages.config
+
+# Tabs Studio
+*.tss
+
+# Telerik's JustMock configuration file
+*.jmconfig
+
+# BizTalk build output
+*.btp.cs
+*.btm.cs
+*.odx.cs
+*.xsd.cs
+
+# OpenCover UI analysis results
+OpenCover/
+
+# Azure Stream Analytics local run output
+ASALocalRun/
+
+# MSBuild Binary and Structured Log
+*.binlog
+
+# NVidia Nsight GPU debugger configuration file
+*.nvuser
+
+# MFractors (Xamarin productivity tool) working folder
+.mfractor/
+
+# Local History for Visual Studio
+.localhistory/
+
+# Visual Studio History (VSHistory) files
+.vshistory/
+
+# BeatPulse healthcheck temp database
+healthchecksdb
+
+# Backup folder for Package Reference Convert tool in Visual Studio 2017
+MigrationBackup/
+
+# Ionide (cross platform F# VS Code tools) working folder
+.ionide/
+
+# Fody - auto-generated XML schema
+FodyWeavers.xsd
+
+# VS Code files for those working on multiple tools
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+*.code-workspace
+
+# Local History for Visual Studio Code
+.history/
+
+# Windows Installer files from build outputs
+*.cab
+*.msi
+*.msix
+*.msm
+*.msp
+
+# JetBrains Rider
+*.sln.iml
+.idea
+
+##
+## Visual studio for Mac
+##
+
+
+# globs
+Makefile.in
+*.userprefs
+*.usertasks
+config.make
+config.status
+aclocal.m4
+install-sh
+autom4te.cache/
+*.tar.gz
+tarballs/
+test-results/
+
+# Mac bundle stuff
+*.dmg
+*.app
+
+# content below from: https://github.com/github/gitignore/blob/master/Global/macOS.gitignore
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+# content below from: https://github.com/github/gitignore/blob/master/Global/Windows.gitignore
+# Windows thumbnail cache files
+Thumbs.db
+ehthumbs.db
+ehthumbs_vista.db
+
+# Dump file
+*.stackdump
+
+# Folder config file
+[Dd]esktop.ini
+
+# Recycle Bin used on file shares
+$RECYCLE.BIN/
+
+# Windows Installer files
+*.cab
+*.msi
+*.msix
+*.msm
+*.msp
+
+# Windows shortcuts
+*.lnk
+
+# Vim temporary swap files
+*.swp

dotnet/05/05a.cs

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+void Main1()
+{
+    var lines = File.ReadAllLines(Path.Join("..", "..", "05a.txt")).Select(l => l.Trim()).ToList();
+    if (lines.Last() == "")
+        lines.RemoveAt(lines.Count - 1);
+
+    List<Rule> rules = new();
+    foreach (var line in lines.TakeWhile(l => !string.IsNullOrWhiteSpace(l)))
+    {
+        var parts = line.Split('|');
+        rules.Add(new(
+            int.Parse(parts[0]),
+            int.Parse(parts[1])
+        ));
+    }
+
+    List<Collection> collections = new();
+    foreach (var line in lines.SkipWhile(l => !string.IsNullOrWhiteSpace(l)).Skip(1))
+    {
+        var parts = line.Split(',').Select(int.Parse);
+        collections.Add(new(parts));
+    }
+
+    int total = 0;
+    foreach (var collection in collections.Where(c => rules.All(r => c.TestRule(r))))
+    {
+        total += collection.Middle();
+    }
+
+    Console.WriteLine(total);
+}
+
+void Main2()
+{
+    var lines = File.ReadAllLines(Path.Join("..", "..", "05a.txt")).Select(l => l.Trim()).ToList();
+    if (lines.Last() == "")
+        lines.RemoveAt(lines.Count - 1);
+
+    List<Rule> rules = new();
+    RuleList rulelist = new();
+    foreach (var line in lines.TakeWhile(l => !string.IsNullOrWhiteSpace(l)))
+    {
+        var parts = line.Split('|');
+        Rule rule = new(
+            int.Parse(parts[0]),
+            int.Parse(parts[1])
+        );
+        rulelist.Add(rule);
+        rules.Add(rule);
+    }
+
+    List<Collection> collections = new();
+    foreach (var line in lines.SkipWhile(l => !string.IsNullOrWhiteSpace(l)).Skip(1))
+    {
+        var parts = line.Split(',').Select(int.Parse);
+        collections.Add(new(parts));
+    }
+
+    var total = 0;
+    var count = 0;
+    foreach (var collection in collections)
+    {
+        var r = collection.Pairs()
+            .Select(p => rulelist.ExtractRule(p.Item1, p.Item2))
+            .Where(r => r is not null)
+            .Select(r => (Rule)r)
+            .ToList();
+        if (!rules.All(collection.TestRule))
+        {
+            collection.Pages.Sort(rulelist.Compare);
+            total += collection.Pages[collection.Pages.Count / 2];
+            count++;
+        }
+    }
+    Console.WriteLine($"Collections: {collections.Count}");
+    Console.WriteLine($"With errors: {count}");
+    Console.WriteLine($"Solution: {total}");
+}
+
+Main2();
+
+record struct Rule(int First, int Second);
+class RuleList
+{
+    Dictionary<(int,int), bool> Rules = new();
+    public RuleList()
+    {
+
+    }
+    public void Add(Rule rule)
+    {
+        bool ordered = rule.First < rule.Second;
+        var pair = ordered
+            ? (rule.First, rule.Second)
+            : (rule.Second, rule.First);
+        Rules.Add(pair, ordered);
+    }
+    //true if correct order, null if no rule
+    public bool? Check(int a, int b)
+    {
+        bool ordered = a < b;
+        var pair = ordered
+            ? (a, b)
+            : (b, a);
+        bool result;
+        return Rules.TryGetValue(pair, out result) ? result ^ ordered : null;
+    }
+    public int Compare(int a, int b)
+    {
+        var check = Check(a, b);
+        if (check is bool _check)
+            return _check ? -1 : 1;
+        return 0;
+    }
+    public Rule? ExtractRule(int a, int b)
+    {
+        var check = Check(a, b);
+        if (check is bool _check)
+            return _check ? new(a, b) : new(b, a);
+        return null;
+    }
+}
+class Collection
+{
+    public readonly List<int> Pages;
+    public Collection(IEnumerable<int> pages)
+    {
+        Pages = pages.ToList();
+    }
+    public bool TestRule(Rule rule)
+    {
+        bool foundFirst = false;
+        bool foundSecond = false;
+        foreach (var page in Pages)
+        {
+            if (page == rule.First)
+            {
+                if (foundSecond)
+                    return false;
+                foundFirst = true;
+            }
+            if (page == rule.Second)
+            {
+                if (foundFirst)
+                    return true;
+                foundSecond = true;
+            }
+        }
+        return true;
+    }
+    public int Middle()
+    {
+        return Pages[Pages.Count / 2];
+    }
+    public List<(int,int)> Pairs()
+    {
+        List<(int,int)> pairs = new();
+        for (int i = 0; i < Pages.Count-1; i++)
+        {
+            for (int j = i+1; j < Pages.Count; j++)
+            {
+                pairs.Add((Pages[i], Pages[j]));
+            }
+        }
+        return pairs;
+    }
+}

dotnet/06/06.cs

@@ -0,0 +1,238 @@
+void Main1()
+{
+    (var map, var pos) = LoadMap(Path.Join("..", "..", "06a.txt"));
+    Guard guard = new(pos, Direction.North);
+    HashSet<(int,int)> visited = new();
+    while (map.InBounds(guard.position))
+    {
+        var next = Next(guard);
+        if (map.Check(next.position))
+        {
+            guard = new(guard.position, guard.direction.Turn());
+            continue;
+        }
+        else
+        {
+            visited.Add(guard.position);
+            guard = next;
+        }
+    }
+    Console.WriteLine(visited.Count());
+}
+
+void Main2()
+{
+    (var map, var pos) = LoadMap(Path.Join("..", "..", "06a.txt"));
+    Guard guard = new(pos, Direction.North);
+    // for (int i = 0; i < 4; i++)
+    // {
+    //     foreach (var obs in map.Obstacles)
+    //     {
+    //         var row = map.GetRow(obs.Item1 + 1).Where(c => c > obs.Item2);
+    //         foreach (var candidate in row)
+    //         {
+    //             var col = map.GetColumn(candidate - 1).Where(r => r > candidate);
+    //             foreach (var third in col)
+    //             {
+    //                 var idea = (third - 1, obs.Item2 - 1);
+    //                 if (!map.Check(idea))
+    //                     map.Ideas.Add(idea);
+    //             }
+    //         }
+    //     }
+    //     map = map.Rotated();
+    // }
+    // Console.WriteLine($"Ideas {map.Ideas.Count()}");
+    int count = 0;
+    // foreach (var idea in map.Ideas)
+    // {
+    //     Guard guard = new(pos, Direction.North);
+    //     // the 5th time the guard hits the obstacle, he must have hit twice from the same side
+    //     int hits = 0;
+    //     while (map.InBounds(guard.position))
+    //     {
+    //         var next = Next(guard);
+    //         if (next.position == idea)
+    //         {
+    //             hits++;
+    //             if (hits >= 5)
+    //             {
+    //                 count++;
+    //                 break;
+    //             }
+    //             guard = new(guard.position, guard.direction.Turn());
+    //         }
+    //         else if (map.Check(next.position))
+    //         {
+    //             guard = new(guard.position, guard.direction.Turn());
+    //         }
+    //         else
+    //         {
+    //             guard = next;
+    //         }
+    //     }
+    // }
+    HashSet<(int,int)> visited = new();
+    int ideaIndex = 0;
+    while (map.InBounds(guard.position))
+    {
+        ideaIndex++;
+        var next = Next(guard);
+        if (map.Check(next.position))
+        {
+            guard = new(guard.position, guard.direction.Turn());
+            continue;
+        }
+        else
+        {
+            visited.Add(guard.position);
+            if (!visited.Contains(next.position) && TestIdea(next.position, guard, map))
+                count++;
+            // Console.WriteLine($"Idea {ideaIndex}");
+            guard = next;
+        }
+    }
+    Console.WriteLine($"Solution {count}");
+}
+
+// Main1();
+Main2();
+
+(Map,(int,int)) LoadMap(string filename)
+{
+    var lines = File.ReadAllLines(filename)
+        .Where(s => !string.IsNullOrWhiteSpace(s))
+        .ToList();
+    var guard = (-1,-1);
+    Map map = new();
+    for (int i = 0; i < lines.Count(); i++)
+    {
+        for (int j = 0; j < lines[i].Count(); j++)
+        {
+            if (lines[i][j] == '#')
+                map.Add((i, j));
+            else if (lines[i][j] == '^')
+                guard = (i, j);
+        }
+    }
+    map.XBound = lines[0].Count();
+    map.YBound = lines.Count();
+    return (map, guard);
+}
+
+bool TestIdea((int,int) idea, Guard guard, Map map)
+{
+    HashSet<Guard> history = new();
+    while (map.InBounds(guard.position))
+    {
+        if (history.Contains(guard))
+            return true;
+        history.Add(guard);
+        var next = Next(guard);
+        if (map.Check(next.position) || next.position == idea)
+        {
+            guard = new(guard.position, guard.direction.Turn());
+        }
+        else
+        {
+            guard = next;
+        }
+    }
+    return false;
+}
+
+//next position IF NO OBSTACLE
+Guard Next(Guard guard)
+{
+    var pos = guard.position;
+    return new(guard.direction switch
+    {
+        Direction.North => (pos.Item1-1, pos.Item2),
+        Direction.East =>  (pos.Item1, pos.Item2+1),
+        Direction.South => (pos.Item1+1, pos.Item2),
+        Direction.West =>  (pos.Item1, pos.Item2-1),
+        _ => throw new Exception(),
+    }, guard.direction);
+}
+
+class Map
+{
+    public HashSet<(int,int)> Obstacles = new();
+    //1 greater than largest value
+    public int XBound = 0;
+    public int YBound = 0;
+    public HashSet<(int,int)> Ideas = new();
+    public Map()
+    {
+
+    }
+    public void Add((int,int) obstacle)
+    {
+        Obstacles.Add(obstacle);
+    }
+    public bool Check((int,int) pos)
+    {
+        return Obstacles.Contains(pos);
+    }
+    public bool InBounds((int,int) pos)
+    {
+        return pos.Item1 >= 0 && pos.Item2 >= 0
+            && pos.Item1 < XBound && pos.Item2 < YBound;
+    }
+    //get list of columns with an obstacle in this row
+    public List<int> GetRow(int row)
+    {
+        List<int> items = [];
+        foreach (var pos in Obstacles)
+        {
+            if (pos.Item1 == row)
+                items.Add(pos.Item2);
+        }
+        items.Sort();
+        return items;
+    }
+    //get list of rows with an obstacle in this column
+    public List<int> GetColumn(int column)
+    {
+        List<int> items = [];
+        foreach (var pos in Obstacles)
+        {
+            if (pos.Item2 == column)
+                items.Add(pos.Item1);
+        }
+        items.Sort();
+        return items;
+    }
+    //counterclockwise rotation
+    public Map Rotated()
+    {
+        (int,int) rotate((int,int) o) => (o.Item2, XBound - o.Item1);
+        Map newmap = new();
+        newmap.Obstacles = new(Obstacles.Select(rotate));
+        newmap.Ideas = new(Ideas.Select(rotate));
+        newmap.XBound = YBound;
+        newmap.YBound = XBound;
+        return newmap;
+    }
+}
+
+enum Direction
+{
+    North,
+    East,
+    South,
+    West,
+}
+readonly record struct Guard((int,int) position, Direction direction);
+
+static class Extensions
+{
+    public static Direction Turn(this Direction direction)
+    {
+        return direction switch
+        {
+            Direction.West => Direction.North,
+            Direction d => d + 1,
+        };
+    }
+}

dotnet/07/07a.cs

@@ -0,0 +1,263 @@
+void Main1()
+{
+    var eqs = LoadEqs(Path.Join("..", "..", "07a.txt"));
+    long total = 0;
+    foreach (var eq in eqs)
+    {
+        if (eq.Test1())
+        {
+            total += eq.Target;
+        }
+    }
+    Console.WriteLine($"Solution {total}");
+}
+
+void Main2()
+{
+    var eqs = LoadEqs(Path.Join("..", "..", "07a.txt"));
+    long total = 0;
+    foreach (var eq in eqs)
+    {
+        if (eq.Test2())
+        {
+            total += eq.Target;
+        }
+    }
+    Console.WriteLine($"Solution1 {total}");
+}
+
+void Main2_take2()
+{
+    var eqs = LoadEqs(Path.Join("..", "..", "07a.txt"));
+    long total = 0;
+    foreach (var eq in eqs)
+    {
+        if (eq.Test3())
+        {
+            total += eq.Target;
+        }
+    }
+    Console.WriteLine($"Solution (exp) {total}");
+}
+
+void Main2_take3()
+{
+    var eqs = LoadEqs(Path.Join("..", "..", "07a.txt"));
+    long total = 0;
+    foreach (var eq in eqs)
+    {
+        if (eq.Test4())
+        {
+            total += eq.Target;
+        }
+    }
+    Console.WriteLine($"Solution       {total}");
+}
+
+void Main2_take2and3()
+{
+    var eqs = LoadEqs(Path.Join("..", "..", "07a.txt"));
+    long total = 0;
+    foreach (var eq in eqs)
+    {
+        var t3 = eq.Test3();
+        var t4 = eq.Test4();
+        if (t3 != t4)
+        {
+            Console.WriteLine((t4 ? "Pass " : "Fail ") + eq.ToString());
+        }
+    }
+}
+
+// Main1();
+Main2();
+// Main2_take2();
+// Main2_take3();
+// Main2_take2and3();
+
+List<EQ> LoadEqs(string filepath)
+{
+    var lines = File.ReadAllLines(filepath).ToList();
+    if (string.IsNullOrWhiteSpace(lines.Last()))
+        lines.RemoveAt(lines.Count()-1);
+    List<EQ> eqs = new();
+    foreach (var line in lines)
+    {
+        var parts = line.Split(':');
+        eqs.Add(new(
+            long.Parse(parts[0]),
+            parts[1].Trim().Split(' ').Select(long.Parse)
+        ));
+    }
+    return eqs;
+}
+
+class EQ
+{
+    public long Target;
+    public List<long> Terms;
+    public EQ(long target, IEnumerable<long> terms)
+    {
+        Target = target;
+        Terms = terms.ToList();
+    }
+    public override string ToString()
+    {
+        return $"{Target}: {string.Join(' ', Terms)}";
+    }
+    public bool Test1()
+    {
+        return InnerTest1(Target, Terms.First(), Terms.Skip(1));
+    }
+    private static bool InnerTest1(long target, long current, IEnumerable<long> terms)
+    {
+        if (current > target)
+            return false;
+        var term = terms.Cast<long?>().FirstOrDefault();
+        if (term is long _term)
+        {
+            return InnerTest1(target, current + _term, terms.Skip(1))
+                || InnerTest1(target, current * _term, terms.Skip(1));
+        }
+        else
+        {
+            return target == current;
+        }
+    }
+    public bool Test2()
+    {
+        return InnerTest2(Target, Terms.First(), Terms, 1);
+    }
+    private static bool InnerTest2(long target, long current, IList<long> terms, int index)
+    {
+        if (current > target)
+            return false;
+        if (index >= terms.Count())
+            return target == current;
+        var term = terms[index];
+        return InnerTest2(target, current + term, terms, index + 1)
+            || InnerTest2(target, current * term, terms, index + 1)
+            || InnerTest2(target, Concat(current, term), terms, index + 1);
+    }
+    public bool Test3()
+    {
+        return InnerTest3(Target, Terms.First(), Terms.Skip(1)) == Result.Success;
+    }
+    private static Result InnerTest3(long target, long current, IEnumerable<long> terms)
+    {
+        if (current > target)
+            return Result.AllOverflow;
+        var term = terms.Cast<long?>().FirstOrDefault();
+        var remaining = terms.Skip(1);
+        if (term is long _term)
+        {
+            return current switch
+            {
+                1 => InnerTest3(target, _term, remaining) switch
+                    {
+                        Result.MixedFailures => InnerTest3(target, 1 + _term, remaining) switch
+                            {
+                                Result.Success => Result.Success,
+                                Result.AllOverflow => Result.MixedFailures,
+                                _ => InnerTest3(target, Concat(1, _term), remaining) switch
+                                    {
+                                        Result.Success => Result.Success,
+                                        _ => Result.MixedFailures,
+                                    },
+                            },
+                        Result res => res,
+                    },
+                0 => InnerTest3(target, 0, remaining) switch
+                    {
+                        Result.MixedFailures => InnerTest3(target, _term, remaining) switch
+                            {
+                                Result.Success => Result.Success,
+                                _ => Result.MixedFailures,
+                            },
+                        Result res => res,
+                    },
+                long _current => _term switch
+                    {
+                        1 => InnerTest3(target, _current, remaining) switch
+                            {
+                                Result.MixedFailures => InnerTest3(target, _current + 1, remaining) switch
+                                    {
+                                        Result.Success => Result.Success,
+                                        Result.MixedFailures => InnerTest3(target, _current * 10 + 1, remaining) switch
+                                            {
+                                                Result.Success => Result.Success,
+                                                _ => Result.MixedFailures,
+                                            },
+                                        _ => Result.MixedFailures,
+                                    },
+                                Result res => res,
+                            },
+                        _ => InnerTest3(target, _current + _term, remaining) switch
+                            {
+                                Result.MixedFailures => InnerTest3(target, _current * _term, remaining) switch
+                                    {
+                                        Result.Success => Result.Success,
+                                        Result.AllOverflow => Result.MixedFailures,
+                                        _ => InnerTest3(target, Concat(_current, _term), remaining) switch
+                                            {
+                                                Result.Success => Result.Success,
+                                                _ => Result.MixedFailures,
+                                            },
+                                    },
+                                Result res => res,
+                            },
+                    },
+            };
+        }
+        else
+        {
+            return (target - current) switch
+            {
+                //should be impossible due to earlier check
+                < 0 => Result.AllOverflow,
+                0   => Result.Success,
+                > 0 => Result.MixedFailures,
+            };
+        }
+    }
+    
+    private static long Concat(long first, long second)
+    {
+        return first * Shift(second) + second;
+    }
+    public bool Test4()
+    {
+        return InnerTest4(Target, Terms, Terms.Count() - 1);
+    }
+    private static bool InnerTest4(long current, IList<long> terms, int index)
+    {
+        long term = terms[index];
+        if (index == 0)
+            return current == term;
+        if (InnerTest4(current - term, terms, index - 1))
+            return true;
+        if (current % term == 0 && InnerTest4(current / term, terms, index - 1))
+            return true;
+        var shift = Shift(term);
+        if ((current % shift == term) && InnerTest4(current / shift, terms, index - 1))
+            return true;
+        return false;
+    }
+    private static long Shift(long num)
+    {
+        var digits = ((long)Math.Log10(num+0.5)) + 1;
+        long shift = 1;
+        while (digits > 0)
+        {
+            shift *= 10;
+            digits--;
+        }
+        return shift;
+    }
+    enum Result
+    {
+        AllOverflow,
+        MixedFailures,
+        Success,
+    }
+}

dotnet/08/08a.cs

@@ -0,0 +1,174 @@
+Main1();
+Main2();
+
+
+void Main1()
+{
+    var map = LoadMap(Path.Join("..", "..", "08a.txt"));
+    HashSet<Point> antinodes = new();
+    foreach (var (ch, points) in map.Antennae)
+    {
+        for (int i = 0; i < points.Count-1; i++)
+        {
+            for (int j = i+1; j < points.Count; j++)
+            {
+                antinodes.UnionWith(points[i].GetAntinodes(points[j]).Where(map.Validate));
+            }
+        }
+    }
+    Console.WriteLine($"Solution {antinodes.Count}");
+}
+
+void Main2()
+{
+    var map = LoadMap(Path.Join("..", "..", "08a.txt"));
+    HashSet<Point> antinodes = new();
+    foreach (var (ch, points) in map.Antennae)
+    {
+        for (int i = 0; i < points.Count-1; i++)
+        {
+            for (int j = i+1; j < points.Count; j++)
+            {
+                antinodes.UnionWith(points[i].GetAntinodes2(points[j], map));
+            }
+        }
+    }
+    Console.WriteLine($"Solution {antinodes.Count}");
+}
+
+Map LoadMap(string filepath)
+{
+    var lines = File.ReadAllLines(filepath)
+        .Where(l => !string.IsNullOrWhiteSpace(l))
+        .Select(s => s.Trim())
+        .ToList();
+    Map map = new();
+    foreach (var (line, row) in lines.Select((l, i) => (l, i)))
+    {
+        foreach (var (c, col) in line.Select((ch, i) => (ch, i)))
+        {
+            if (c != '.')
+            {
+                Point p = new(row, col);
+                if (map.Antennae.TryGetValue(c, out var points))
+                {
+                    points.Add(p);
+                }
+                else
+                {
+                    map.Antennae[c] = new(Enumerable.Repeat(p, 1));
+                }
+            }
+        }
+    }
+    map.Width = lines[0].Length;
+    map.Height = lines.Count;
+    return map;
+}
+
+public static class Stuff
+{
+    //I forgot the good algorithm
+    public static int TerribleGcf(int first, int second)
+    {
+        int gcf = 1;
+        while (first % 2 == 0 && second % 2 == 0)
+        {
+            gcf *= 2;
+            first /= 2;
+            second /= 2;
+        }
+        for (int prime = 3; prime < first && prime < second; prime += 2)
+        {
+            while (first % prime == 0 && second % prime == 0)
+            {
+                gcf *= prime;
+                first /= prime;
+                second /= prime;
+            }
+        }
+        return gcf;
+    }
+    //I had to look up the right way
+    public static int EuclideanGcf(int first, int second)
+    {
+        if (first == 0 || second == 0)
+            return 0;
+        first = Math.Abs(first);
+        second = Math.Abs(second);
+        while (first != second)
+        {
+            if (second > first)
+            {
+                first = first ^ second;
+                second = first ^ second;
+                first = first ^ second;
+            }
+            first = first - second;
+        }
+        return first;
+    }
+}
+
+class Map
+{
+    public Dictionary<char, List<Point>> Antennae = new();
+    public int Width;
+    public int Height;
+    public Map()
+    {
+
+    }
+    public bool Validate(Point p)
+        => p.Row >= 0 && p.Row < Width && p.Col >= 0 && p.Col < Height;
+}
+
+record struct Point(int Row, int Col)
+{
+    public static Vector operator -(Point first, Point second)
+        => new(first.Row - second.Row, first.Col - second.Col);
+    public static Point operator +(Point first, Vector second)
+        => new(first.Row + second.Row, first.Col + second.Col);
+    public static Point operator -(Point first, Vector second)
+        => new(first.Row - second.Row, first.Col - second.Col);
+    public readonly IEnumerable<Point> GetAntinodes(Point other)
+    {
+        var diff = this - other;
+        yield return this + diff;
+        yield return other - diff;
+        if (diff.Row % 3 == 0 && diff.Col % 3 == 0)
+        {
+            Console.WriteLine("inline");
+            yield return other + (diff / 3);
+            yield return other + (diff * 2 / 3);
+        }
+    }
+    public IEnumerable<Point> GetAntinodes2(Point other, Map map)
+    {
+        var diff = this - other;
+        // diff /= Stuff.TerribleGcf(diff.Row, diff.Col);
+        diff /= Stuff.EuclideanGcf(diff.Row, diff.Col);
+        var running = this;
+        while (map.Validate(running))
+        {
+            yield return running;
+            running -= diff;
+        }
+        running = this + diff;
+        while (map.Validate(running))
+        {
+            yield return running;
+            running += diff;
+        }
+    }
+}
+
+record struct Vector(int Row, int Col)
+{
+    public static Vector operator +(Vector first, Vector second)
+        => new(first.Row + second.Row, first.Col + second.Col);
+    public static Vector operator *(Vector first, int second)
+        => new(first.Row * second, first.Col * second);
+    public static Vector operator /(Vector first, int second)
+        => new(first.Row / second, first.Col / second);
+}

dotnet/09/09.cs

@@ -0,0 +1,138 @@
+using System.Numerics;
+using System.Security.Cryptography.X509Certificates;
+
+// Main1();
+Main2();
+
+void Main1()
+{
+    var data = LoadData1(Path.Join("..", "..", "09a.txt"));
+    int i = 0;
+    int j = data.Length - 1;
+    while (i < j)
+    {
+        if (data[i] == -1)
+        {
+            while (data[j] == -1)
+                j--;
+            data[i] = data[j];
+            data[j] = -1;
+        }
+        i++;
+    }
+    i--;
+    BigInteger checksum = 0;
+    while (i >= 0)
+    {
+        if (data[i] < 0)
+            throw new Exception($"Index {i} Value {data[i]}");
+        checksum += i * data[i];
+        i--;
+    }
+    Console.WriteLine($"Part1: {checksum,15}");
+}
+
+void Main2()
+{
+    var (files, empties) = LoadData2(Path.Join("..", "..", "09a.txt"));
+    for (int i = files.Count-1; i >= 1; i--)
+    {
+        var file = files[i];
+        for (int j = 0; j < empties.Count; j++)
+        {
+            var empty = empties[j];
+            if (file.Location < empty.Location)
+                break;
+            if (file.Length <= empty.Length)
+            {
+                file.Location = empty.Location;
+                empties[j] = new(empty.Location + file.Length, empty.Length - file.Length);
+                break;
+            }
+        }
+    }
+    //long is big enough but changing it didn't help execution time so...
+    BigInteger checksum = 0;
+    foreach (var f in files)
+    {
+        for (int i = 0; i < f.Length; i++)
+        {
+            checksum += f.Id * (f.Location + i);
+        }
+    }
+    Console.WriteLine($"Part2: {checksum,15}");
+}
+
+int[] LoadData1(string filepath)
+{
+    int next_id = 0;
+    bool next_is_blank = false;
+    int GetId()
+    {
+        if (next_is_blank)
+        {
+            next_is_blank = false;
+            return -1;
+        }
+        else
+        {
+            next_is_blank = true;
+            return next_id++;
+        }
+    }
+    var data = File.ReadAllText(filepath).Trim().SelectMany(c => Enumerable.Repeat(GetId(), c - '0')).ToArray();
+    return data;
+}
+
+(List<Filelike>,List<Empty>) LoadData2(string filepath)
+{
+    short next_id = 0;
+    bool next_is_blank = false;
+    int location = 0;
+    List<Filelike> files = [];
+    List<Empty> empties = [];
+    foreach (char c in File.ReadAllText(filepath).Trim())
+    {
+        int length = c - '0';
+        if (next_is_blank)
+        {
+            if (length > 0)
+                empties.Add(new (location, length));
+            next_is_blank = false;
+            location += length;
+        }
+        else
+        {
+            next_is_blank = true;
+            if (length > 0)
+                files.Add(new (location, length, next_id));
+            location += length;
+            next_id++;
+        }
+    }
+    return (files,empties);
+}
+
+class Filelike(int Location, int Length, short Id)
+{
+    public int Location = Location;
+    public int Length = Length;
+    public short Id = Id;
+}
+class Empty(int Location, int Length)
+{
+    public int Location = Location;
+    public int Length = Length;
+}
+
+// class Filelike(int Location, int Length, int Id)
+// {
+//     public int Location = Location;
+//     public int Length = Length;
+//     public int Id = Id;
+// }
+// class Empty(int Location, int Length)
+// {
+//     public int Location = Location;
+//     public int Length = Length;
+// }