part one complete

AdventOfCode2025/AdventOfCode2025.csproj

@@ -24,6 +24,22 @@
       <Content Include="Input\DayThree.txt">
         <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
       </Content>
+      <None Remove="Input\DayFour.txt" />
+      <Content Include="Input\DayFour.txt">
+        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </Content>
+      <None Remove="Input\DayFive.txt" />
+      <Content Include="Input\DayFive.txt">
+        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </Content>
+      <None Remove="Input\DaySix.txt" />
+      <Content Include="Input\DaySix.txt">
+        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </Content>
+      <None Remove="Input\DaySeven.txt" />
+      <Content Include="Input\DaySeven.txt">
+        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </Content>
     </ItemGroup>
 
 </Project>

AdventOfCode2025/Cafeteria.cs

@@ -0,0 +1,80 @@
+using AdventOfCode2025.Utils;
+using Range = AdventOfCode2025.Utils.Range;
+
+namespace AdventOfCode2025;
+
+public class Cafeteria : IAdventSolution
+{
+    public AdventSolution Solve(string input)
+    {
+        var lines = input.SplitLines();
+
+        var ranges = new HashSet<Range>();
+        var startIndex = 0;
+        while (lines[startIndex].Contains('-'))
+        {
+            var line = lines[startIndex++];
+            var parts = line.Split('-');
+            var range = new Range(ulong.Parse(parts[0]), ulong.Parse(parts[1]));
+            AddRange(ranges, range);
+        }
+        
+        var fresh = 0;
+        for(; startIndex < lines.Length; startIndex++)
+        {
+            var line = lines[startIndex];
+            if (line.Contains('-'))
+                continue;
+
+            var num = ulong.Parse(line);
+            if(ranges.Any(x => x.IsInRange(num))) fresh++;
+        }
+        RemoveExtraRanges(ranges);
+        var totalFresh = 0UL;
+        foreach (var range in ranges)
+            totalFresh += range.InclusiveCount;
+        
+        return new AdventSolution(fresh.ToString(), totalFresh.ToString());
+    }
+
+    private void AddRange(HashSet<Range> ranges, Range range)
+    {
+        var first = ranges.FirstOrDefault(x => x.IsInRange(range.Min));
+        if (first != default)
+        {
+            ranges.Remove(first);
+            if(!first.IsInRange(range.Max)) 
+                first =  new Range(first.Min, range.Max);
+        }
+        else
+            first = range;
+        
+        var last = ranges.LastOrDefault(x => x.IsInRange(first.Max));
+        if (last != default)
+        {
+            ranges.Remove(last);
+            if (!last.IsInRange(first.Min))
+                last = new Range(first.Min,  last.Max);
+        }
+        else
+            last = first;
+        
+        ranges.Add(last);
+    }
+
+    private void RemoveExtraRanges(HashSet<Range> ranges)
+    {
+        var toRemove = new List<Range>();
+        foreach (var range in ranges)
+        {
+            if(ranges.Any(x => x != range && (x.IsInRange(range.Min) || x.IsInRange(range.Max))))
+                toRemove.Add(range);
+        }
+
+        foreach (var remove in toRemove)
+        {
+            ranges.Remove(remove);
+            AddRange(ranges, remove);
+        }
+    }
+}

AdventOfCode2025/GiftShop.cs

@@ -1,4 +1,5 @@
 using System.Text.RegularExpressions;
+using Range = AdventOfCode2025.Utils.Range;
 
 namespace AdventOfCode2025;
 
@@ -44,5 +45,3 @@ public class GiftShop : IAdventSolution
         return new Range(ulong.Parse(numbers[0]), ulong.Parse(numbers[^1]));
     }
 }
-
-public record struct Range(ulong Min, ulong Max);

AdventOfCode2025/Laboratories.cs

@@ -0,0 +1,32 @@
+using AdventOfCode2025.Utils;
+
+namespace AdventOfCode2025;
+
+public class Laboratories : IAdventSolution
+{
+    public AdventSolution Solve(string input)
+    {
+        var lines = input.SplitLines();
+        var start = lines[0].IndexOf('S');
+        var splitters = new HashSet<Coordinate>();
+        var origin = new Coordinate(start, 0);
+        Traverse(lines, origin, splitters);
+        return new AdventSolution(splitters.Count.ToString(), null);
+    }
+
+    private void Traverse(string[] map, Coordinate start, HashSet<Coordinate> splitters)
+    {
+        if (start.X < 0 || start.X >= map[0].Length)
+            return;
+        
+        for (var y = start.Y; y < map.Length; y++)
+        {
+            if (map[y][start.X] != '^') continue;
+            if (!splitters.Add(new Coordinate(start.X, y))) return;
+            
+            Traverse(map, new Coordinate(start.X + 1, y), splitters);
+            Traverse(map, new Coordinate(start.X - 1, y), splitters);
+            return;
+        }
+    }
+}

AdventOfCode2025/Lobby.cs

@@ -8,10 +8,13 @@ public class Lobby : IAdventSolution
     public AdventSolution Solve(string input)
     {
         var lines = input.SplitLines();
-        var total = 0;
+        var total = 0UL;
+        var total2 = 0UL;
         foreach (var line in lines)
         {
-            var first = '0';
+            total += GreatestXDigits(line, 2);
+            total2 += GreatestXDigits(line, 12);
+            /*var first = '0';
             var second = '0';
             for (var i = 0; i < line.Length; i++)
             {
@@ -25,11 +28,41 @@ public class Lobby : IAdventSolution
                     second = line[i];
                 }
             }
-            
+            total += int.Parse($"{first}{second}");*/
-            
-            total += int.Parse($"{first}{second}");
         }
         
-        return new AdventSolution(total.ToString(), null);
+        return new AdventSolution(total.ToString(), total2.ToString());
+    }
+
+    private readonly List<char> _chars = new();
+
+    private ulong GreatestXDigits(string input, int digits)
+    {
+        _chars.Clear();
+        _chars.Add(input[0]);
+        for (var i = 1; i < input.Length; i++)
+        {
+            var remainingChars = input.Length - i - 1;
+            var c = input[i];
+            if(!IsReplace(c, remainingChars, digits) && _chars.Count < digits)
+            {
+                _chars.Add(c);
+            }
+        }
+        
+        return ulong.Parse(string.Join("", _chars));
+    }
+
+    private bool IsReplace(char c, int remaining, int digits)
+    {
+        for (var i = 0; i < _chars.Count; i++)
+        {
+            if (c <= _chars[i] || (remaining < digits - (i+1))) continue;
+            _chars.RemoveRange(i, _chars.Count - i);
+            _chars.Add(c);
+            return true;
+        }
+
+        return false;
     }
 }

AdventOfCode2025/PrintingDepartment.cs

@@ -0,0 +1,57 @@
+using AdventOfCode2025.Utils;
+
+namespace AdventOfCode2025;
+
+public class PrintingDepartment : IAdventSolution
+{
+    private readonly HashSet<Coordinate> _existingRolls = new();
+    public AdventSolution Solve(string input)
+    {
+        var map = input.SplitLines();
+        for (var i = 0; i < map.Length; i++)
+        {
+            for (var j = 0; j < map[i].Length; j++)
+            {
+                if(map[i][j] != '.')
+                    _existingRolls.Add(new Coordinate(j, i));
+            }
+        }
+        var initialCount = _existingRolls.Count;
+        var accessible = -1;
+        var firstAccessible = -1;
+        var toRemove = new HashSet<Coordinate>();
+        while(accessible != 0 && _existingRolls.Count > 0)
+        {
+            accessible = 0;
+            foreach (var c in _existingRolls)
+            {
+                if (!IsAccessible(c)) continue;
+                accessible++;
+                toRemove.Add(c);
+            }
+            
+            if (firstAccessible == -1) firstAccessible = accessible;
+            
+            _existingRolls.RemoveWhere(x => toRemove.Contains(x));
+            toRemove.Clear();
+        } 
+
+        return new AdventSolution(firstAccessible.ToString(), (initialCount - _existingRolls.Count).ToString());
+    }
+
+    private readonly Coordinate[] _directions =
+    [
+        new(-1, -1), new( 0, -1), new( 1, -1),
+        new(-1,  0),              new( 1,  0),
+        new(-1,  1), new( 0,  1), new( 1,  1)
+    ];
+    private bool IsAccessible(Coordinate position)
+    {
+        var neighbors = 0;
+        foreach (var dir in _directions)
+        {
+            if(_existingRolls.Contains(position + dir)) neighbors++;
+        }
+        return neighbors < 4;
+    }
+}

AdventOfCode2025/Program.cs

@@ -10,3 +10,15 @@ AdventSolver<GiftShop>.Solve(dayTwoInput, 2, "Gift Shop");
 
 var dayThreeInput = await File.ReadAllTextAsync("./Input/DayThree.txt");
 AdventSolver<Lobby>.Solve(dayThreeInput, 3, "Lobby");
+
+var dayFourInput = await File.ReadAllTextAsync("./Input/DayFour.txt");
+AdventSolver<PrintingDepartment>.Solve(dayFourInput, 4, "Printing Department");
+
+var dayFiveInput = await File.ReadAllTextAsync("./Input/DayFive.txt");
+AdventSolver<Cafeteria>.Solve(dayFiveInput, 5, "Cafeteria");
+
+var daySixInput = await File.ReadAllTextAsync("./Input/DaySix.txt");
+AdventSolver<TrashCompactor>.Solve(daySixInput, 6, "Trash Compactor");
+
+var daySevenInput = await File.ReadAllTextAsync("./Input/DaySeven.txt");
+AdventSolver<Laboratories>.Solve(daySevenInput, 7, "Laboratories");

AdventOfCode2025/TrashCompactor.cs

@@ -0,0 +1,34 @@
+using AdventOfCode2025.Utils;
+
+namespace AdventOfCode2025;
+
+public class TrashCompactor : IAdventSolution
+{
+    public AdventSolution Solve(string input)
+    {
+        var lines = input.SplitLines();
+        var operators = lines[^1].Split(' ',  StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+        var results = new ulong[operators.Length];
+        for (var i = 0; i < lines.Length - 1; i++)
+        {
+            var line = lines[i].Split(' ',  StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+            for (var j = 0; j < line.Length; j++)
+            {
+                if(i == 0)
+                    results[j] = ulong.Parse(line[j]);
+                else switch (operators[j])
+                {
+                    case "+":
+                        results[j] += ulong.Parse(line[j]);
+                        break;
+                    case "*":
+                        results[j] *= ulong.Parse(line[j]);
+                        break;
+                }
+            }
+        }
+        var sum = results.Aggregate(0UL, (current, result) => current + result);
+
+        return new AdventSolution(sum.ToString(),null);
+    }
+}

AdventOfCode2025/Utils/Coordinate.cs

@@ -0,0 +1,16 @@
+using System.Numerics;
+
+namespace AdventOfCode2025.Utils;
+
+public record struct Coordinate(int X, int Y) : IAdditionOperators<Coordinate,Coordinate,Coordinate>, ISubtractionOperators<Coordinate,Coordinate,Coordinate>
+{
+    public static Coordinate operator +(Coordinate left, Coordinate right)
+    {
+        return new Coordinate(left.X + right.X, left.Y + right.Y);
+    }
+
+    public static Coordinate operator -(Coordinate left, Coordinate right)
+    {
+        return new Coordinate(left.X - right.X, left.Y - right.Y);
+    }
+}

AdventOfCode2025/Utils/Range.cs

@@ -0,0 +1,8 @@
+namespace AdventOfCode2025.Utils;
+
+public record struct Range(ulong Min, ulong Max)
+{
+    public ulong InclusiveCount => Max - Min + 1;
+    
+    public bool IsInRange(ulong value) => value >= Min && value <= Max;
+}