Added solution for "Day 11: Cosmic Expansion", part 2

README.md

@@ -80,6 +80,14 @@ The input data is such that there are only two pipes pointing to *S*, so it find
 
 For part 2, I tracked tiles that are "left" and "right" of the path the algorithm took, and implemented a little flood-fill algorithm that tries to fill the area in between the "left" tiles and the "right" tiles, while counting them. The "outside" group is the one where the flood-fill touches the edge of the map and is simply ignored.
 
+## Day 11: Cosmic Expansion
+
+<https://adventofcode.com/2023/day/11>
+
+While parsing the input, we track coordinates of each galaxy, and for each row and column a *1* if it is empty and a *0* if not. At the end we sum for each pair of galaxies the values for each row and column between their coordinates *+1* to get the sum of their (Manhattan) distances.
+
+This approach was trivial to adapt for part 2, since all that was needed was another factor that had to be multiplied with the values tracked for the rows and columns before applying the *+1*.
+
 ## License
 
 Copyright (C) 2023 Stefan Müller

solvers/UCosmicExpansion.pas

@@ -26,8 +26,8 @@ uses
 
 const
   CGalaxyChar = '#';
-  CEmptySpaceFactor = 2;
-  CNonEmptySpaceFactor = 1;
+  CEmptySpaceFactor = 1;
+  CNonEmptySpaceFactor = 0;
 
 type
 
@@ -45,6 +45,7 @@ type
     procedure Finish; override;
     function GetDataFileName: string; override;
     function GetPuzzleName: string; override;
+    function GetExpansionFactor: Integer; virtual;
   end;
 
 implementation
@@ -107,9 +108,15 @@ begin
   for i := 0 to FGalaxies.Count - 1 do
     for j := i + 1 to FGalaxies.Count - 1 do begin
       for k := Min(FGalaxies[i].X, FGalaxies[j].X) to Max(FGalaxies[i].X, FGalaxies[j].X) - 1 do
-        Inc(FPart1, FColumnExpansion[k]);
+      begin
+        Inc(FPart1, 1 + FColumnExpansion[k]);
+        Inc(FPart2, 1 + FColumnExpansion[k] * GetExpansionFactor);
+      end;
       for k := Min(FGalaxies[i].Y, FGalaxies[j].Y) + 1 to Max(FGalaxies[i].Y, FGalaxies[j].Y) do
-        Inc(FPart1, FRowExpansion[k]);
+      begin
+        Inc(FPart1, 1 + FRowExpansion[k]);
+        Inc(FPart2, 1 + FRowExpansion[k] * GetExpansionFactor);
+      end;
     end;
 end;
 
@@ -123,5 +130,10 @@ begin
    Result := 'Day 11: Cosmic Expansion';
 end;
 
+function TCosmicExpansion.GetExpansionFactor: Integer;
+begin
+  Result := 999999;
+end;
+
 end.
 

tests/UCosmicExpansionTestCases.pas

@@ -33,6 +33,7 @@ type
     function CreateSolver: ISolver; override;
   published
     procedure TestPart1;
+    procedure TestPart2;
   end;
 
   { TCosmicExpansionExampleTestCase }
@@ -44,6 +45,36 @@ type
     procedure TestPart1;
   end;
 
+  { TFactor10CosmicExpansion }
+
+  TFactor10CosmicExpansion = class(TCosmicExpansion)
+    function GetExpansionFactor: Integer; override;
+  end;
+
+  { TCosmicExpansionExampleFactor10TestCase }
+
+  TCosmicExpansionExampleFactor10TestCase = class(TExampleEngineBaseTest)
+  protected
+    function CreateSolver: ISolver; override;
+  published
+    procedure TestPart2;
+  end;
+
+  { TFactor100CosmicExpansion }
+
+  TFactor100CosmicExpansion = class(TCosmicExpansion)
+    function GetExpansionFactor: Integer; override;
+  end;
+
+  { TCosmicExpansionExampleFactor100TestCase }
+
+  TCosmicExpansionExampleFactor100TestCase = class(TExampleEngineBaseTest)
+  protected
+    function CreateSolver: ISolver; override;
+  published
+    procedure TestPart2;
+  end;
+
 implementation
 
 { TCosmicExpansionFullDataTestCase }
@@ -58,6 +89,11 @@ begin
   AssertEquals(9686930, FSolver.GetResultPart1);
 end;
 
+procedure TCosmicExpansionFullDataTestCase.TestPart2;
+begin
+  AssertEquals(630728425490, FSolver.GetResultPart2);
+end;
+
 { TCosmicExpansionExampleTestCase }
 
 function TCosmicExpansionExampleTestCase.CreateSolver: ISolver;
@@ -70,9 +106,49 @@ begin
   AssertEquals(374, FSolver.GetResultPart1);
 end;
 
+{ TFactor10CosmicExpansion }
+
+function TFactor10CosmicExpansion.GetExpansionFactor: Integer;
+begin
+  Result := 9;
+end;
+
+{ TCosmicExpansionExampleFactor10TestCase }
+
+function TCosmicExpansionExampleFactor10TestCase.CreateSolver: ISolver;
+begin
+  Result := TFactor10CosmicExpansion.Create;
+end;
+
+procedure TCosmicExpansionExampleFactor10TestCase.TestPart2;
+begin
+  AssertEquals(1030, FSolver.GetResultPart2);
+end;
+
+{ TFactor100CosmicExpansion }
+
+function TFactor100CosmicExpansion.GetExpansionFactor: Integer;
+begin
+  Result := 99;
+end;
+
+{ TCosmicExpansionExampleFactor100TestCase }
+
+function TCosmicExpansionExampleFactor100TestCase.CreateSolver: ISolver;
+begin
+  Result := TFactor100CosmicExpansion.Create;
+end;
+
+procedure TCosmicExpansionExampleFactor100TestCase.TestPart2;
+begin
+  AssertEquals(8410, FSolver.GetResultPart2);
+end;
+
 initialization
 
   RegisterTest(TCosmicExpansionFullDataTestCase);
   RegisterTest(TCosmicExpansionExampleTestCase);
+  RegisterTest(TCosmicExpansionExampleFactor10TestCase);
+  RegisterTest(TCosmicExpansionExampleFactor100TestCase);
 end.