Added solution for "Day 23: A Long Walk", part 1
This commit is contained in:
parent
c3ecaf59fa
commit
5495b32692
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@ -129,6 +129,10 @@
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<Filename Value="solvers\USandSlabs.pas"/>
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<IsPartOfProject Value="True"/>
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</Unit>
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<Unit>
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<Filename Value="solvers\ULongWalk.pas"/>
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<IsPartOfProject Value="True"/>
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</Unit>
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</Units>
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</ProjectOptions>
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<CompilerOptions>
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@ -27,7 +27,7 @@ uses
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UTrebuchet, UCubeConundrum, UGearRatios, UScratchcards, UGiveSeedFertilizer, UWaitForIt, UCamelCards,
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UHauntedWasteland, UNumberTheory, UMirageMaintenance, UPipeMaze, UCosmicExpansion, UHotSprings, UPointOfIncidence,
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UParabolicReflectorDish, ULensLibrary, UFloorWillBeLava, UClumsyCrucible, ULavaductLagoon, UAplenty,
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UPulsePropagation, UStepCounter, USandSlabs;
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UPulsePropagation, UStepCounter, USandSlabs, ULongWalk;
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type
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@ -91,6 +91,7 @@ begin
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20: engine.RunAndFree(TPulsePropagation.Create);
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21: engine.RunAndFree(TStepCounter.Create);
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22: engine.RunAndFree(TSandSlabs.Create);
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23: engine.RunAndFree(TLongWalk.Create);
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end;
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engine.Free;
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@ -0,0 +1,321 @@
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{
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Solutions to the Advent Of Code.
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Copyright (C) 2023 Stefan Müller
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This program is free software: you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program. If not, see <http://www.gnu.org/licenses/>.
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}
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unit ULongWalk;
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{$mode ObjFPC}{$H+}
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interface
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uses
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Classes, SysUtils, Generics.Collections, USolver;
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type
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TPoints = specialize TList<TPoint>;
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TCrossing = class;
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{ TPath }
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TPath = class
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private
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FEnd: TCrossing;
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FLength: Integer;
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public
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property EndCrossing: TCrossing read FEnd;
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property Length: Integer read FLength;
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constructor Create(const ALength: Integer; const AEnd: TCrossing);
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end;
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TPaths = specialize TObjectList<TPath>;
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{ TPathStart }
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TPathStart = record
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Position, ReverseDirection: TPoint;
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Crossing: TCrossing;
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end;
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TPathStartQueue = specialize TQueue<TPathStart>;
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{ TCrossing }
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TCrossing = class
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private
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FPosition: TPoint;
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FOutPaths: TPaths;
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FDistance: Integer;
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public
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property Position: TPoint read FPosition;
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property OutPaths: TPaths read FOutPaths;
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property Distance: Integer read FDistance write FDistance;
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constructor Create(constref APosition: TPoint);
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destructor Destroy; override;
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procedure AddOutPath(const AOutPath: TPath);
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end;
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TCrossings = specialize TObjectList<TCrossing>;
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TCrossingStack = specialize TStack<TCrossing>;
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{ TLongWalk }
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TLongWalk = class(TSolver)
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private
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FLines: TStringList;
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FPaths: TPaths;
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FCrossings, FWaitingForOtherInPath: TCrossings;
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FStart: TCrossing;
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function GetPosition(constref APoint: TPoint): Char;
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procedure ProcessPaths;
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procedure StepPath(const AStartPositionQueue: TPathStartQueue);
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function FindOrCreateCrossing(constref APosition: TPoint; const AStartPositionQueue: TPathStartQueue): TCrossing;
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procedure FindLongestPath;
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public
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constructor Create;
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destructor Destroy; override;
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procedure ProcessDataLine(const ALine: string); override;
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procedure Finish; override;
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function GetDataFileName: string; override;
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function GetPuzzleName: string; override;
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end;
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TDirection = (dirRight, dirDown, dirLeft, dirUp);
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const
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CPathChar = '.';
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CForestChar = '#';
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CRightSlopeChar = '>';
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CDownSlopeChar = 'v';
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CDirections: array[TDirection] of TPoint = ((X: 1; Y: 0), (X: 0; Y: 1), (X: -1; Y: 0), (X: 0; Y: -1));
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CStartReverseDirection: TPoint = (X: 0; Y: -1);
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implementation
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{ TPath }
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constructor TPath.Create(const ALength: Integer; const AEnd: TCrossing);
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begin
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FLength := ALength;
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FEnd := AEnd;
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end;
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{ TCrossing }
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constructor TCrossing.Create(constref APosition: TPoint);
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begin
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FPosition := APosition;
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FOutPaths := TPaths.Create(False);
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FDistance := 0;
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end;
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destructor TCrossing.Destroy;
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begin
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FOutPaths.Free;
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inherited Destroy;
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end;
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procedure TCrossing.AddOutPath(const AOutPath: TPath);
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begin
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FOutPaths.Add(AOutPath);
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end;
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{ TLongWalk }
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function TLongWalk.GetPosition(constref APoint: TPoint): Char;
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begin
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Result := FLines[APoint.Y][APoint.X];
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end;
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procedure TLongWalk.ProcessPaths;
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var
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stack: TPathStartQueue;
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pathStart: TPathStart;
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begin
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stack := TPathStartQueue.Create;
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pathStart.Position := FStart.Position;
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pathStart.Crossing := FStart;
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pathStart.ReverseDirection := CStartReverseDirection;
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stack.Enqueue(pathStart);
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while stack.Count > 0 do
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StepPath(stack);
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stack.Free;
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end;
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procedure TLongWalk.StepPath(const AStartPositionQueue: TPathStartQueue);
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var
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start: TPathStart;
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new, direction: TPoint;
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c: Char;
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len: Integer;
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oneMore, stop: Boolean;
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crossing: TCrossing;
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path: TPath;
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begin
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start := AStartPositionQueue.Dequeue;
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len := 1;
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if start.Crossing <> FStart then
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Inc(len);
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oneMore := False;
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stop := False;
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repeat
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for direction in CDirections do
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if direction <> start.ReverseDirection then
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begin
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new := start.Position + direction;
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c := GetPosition(new);
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if c <> CForestChar then
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begin
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start.ReverseDirection := Point(-direction.X, -direction.Y);
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start.Position := new;
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if oneMore or (new.Y = FLines.Count - 1) then
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stop := True
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else
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Inc(len);
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if c <> CPathChar then
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oneMore := True;
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Break;
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end;
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end;
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until stop;
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crossing := FindOrCreateCrossing(start.Position, AStartPositionQueue);
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path := TPath.Create(len, crossing);
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FPaths.Add(path);
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start.Crossing.AddOutPath(path);
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end;
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// Crossing with multiple (two) entries will only be added to FCrossings once both in-paths have been processed. This
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// guarantees a topological order in the list of crossings, which is required for our longest path algorithm.
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function TLongWalk.FindOrCreateCrossing(constref APosition: TPoint; const AStartPositionQueue: TPathStartQueue):
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TCrossing;
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var
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i: Integer;
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pathStart: TPathStart;
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begin
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Result := nil;
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// Checks if the crossing has already been encountered.
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i := 0;
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while (i < FWaitingForOtherInPath.Count) and (Result = nil) do
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begin
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if FWaitingForOtherInPath[i].Position = APosition then
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begin
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Result := FWaitingForOtherInPath[i];
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FCrossings.Add(Result);
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end
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else
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Inc(i);
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end;
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if Result <> nil then
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begin
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FWaitingForOtherInPath.Delete(i);
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Exit;
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end;
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// Creates a new crossing.
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Result := TCrossing.Create(APosition);
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// Checks if the new crossing has multiple entries.
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if (GetPosition(APosition + CDirections[dirLeft]) = CRightSlopeChar)
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and (GetPosition(APosition + CDirections[dirUp]) = CDownSlopeChar) then
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FWaitingForOtherInPath.Add(Result)
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else
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FCrossings.Add(Result);
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if APosition.Y < FLines.Count - 1 then
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begin
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// Adds the exits of this crossing to the stack as starts for new paths.
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pathStart.Crossing := Result;
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pathStart.Position := APosition + CDirections[dirRight];
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if GetPosition(pathStart.Position) = CRightSlopeChar then
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begin
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pathStart.ReverseDirection := CDirections[dirLeft];
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AStartPositionQueue.Enqueue(pathStart);
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end;
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pathStart.Position := APosition + CDirections[dirDown];
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if GetPosition(pathStart.Position) = CDownSlopeChar then
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begin
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pathStart.ReverseDirection := CDirections[dirUp];
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AStartPositionQueue.Enqueue(pathStart);
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end;
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end
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end;
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procedure TLongWalk.FindLongestPath;
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var
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crossing: TCrossing;
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path: TPath;
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begin
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for crossing in FCrossings do
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begin
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for path in crossing.OutPaths do
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if path.EndCrossing.Distance < crossing.Distance + path.Length then
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path.EndCrossing.Distance := crossing.Distance + path.Length;
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end;
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FPart1 := FCrossings.Last.Distance;
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end;
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constructor TLongWalk.Create;
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begin
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FLines := TStringList.Create;
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FPaths := TPaths.Create;
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FCrossings := TCrossings.Create;
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FWaitingForOtherInPath := TCrossings.Create(False);
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end;
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destructor TLongWalk.Destroy;
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begin
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FLines.Free;
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FPaths.Free;
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FCrossings.Free;
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FWaitingForOtherInPath.Free;
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inherited Destroy;
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end;
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procedure TLongWalk.ProcessDataLine(const ALine: string);
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begin
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if FLines.Count = 0 then
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begin
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FStart := TCrossing.Create(Point(ALine.IndexOf(CPathChar) + 1, 0));
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FCrossings.Add(FStart);
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end;
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FLines.Add(ALine);
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end;
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procedure TLongWalk.Finish;
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begin
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ProcessPaths;
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FindLongestPath;
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end;
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function TLongWalk.GetDataFileName: string;
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begin
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Result := 'long_walk.txt';
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end;
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function TLongWalk.GetPuzzleName: string;
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begin
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Result := 'Day 23: A Long Walk';
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end;
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end.
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@ -132,6 +132,10 @@
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<Filename Value="USandSlabsTestCases.pas"/>
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<IsPartOfProject Value="True"/>
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</Unit>
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<Unit>
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<Filename Value="ULongWalkTestCases.pas"/>
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<IsPartOfProject Value="True"/>
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</Unit>
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</Units>
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</ProjectOptions>
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<CompilerOptions>
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@ -8,7 +8,7 @@ uses
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UHauntedWastelandTestCases, UMirageMaintenanceTestCases, UPipeMazeTestCases, UCosmicExpansionTestCases,
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UHotSpringsTestCases, UPointOfIncidenceTestCases, UParabolicReflectorDishTestCases, ULensLibraryTestCases,
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UFloorWillBeLavaTestCases, UClumsyCrucibleTestCases, ULavaductLagoonTestCases, UAplentyTestCases,
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UPulsePropagationTestCases, UStepCounterTestCases, USandSlabsTestCases;
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UPulsePropagationTestCases, UStepCounterTestCases, USandSlabsTestCases, ULongWalkTestCases;
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{$R *.res}
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@ -0,0 +1,78 @@
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{
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Solutions to the Advent Of Code.
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Copyright (C) 2023 Stefan Müller
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This program is free software: you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program. If not, see <http://www.gnu.org/licenses/>.
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}
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unit ULongWalkTestCases;
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{$mode ObjFPC}{$H+}
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interface
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uses
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Classes, SysUtils, fpcunit, testregistry, USolver, UBaseTestCases, ULongWalk;
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type
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{ TLongWalkFullDataTestCase }
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TLongWalkFullDataTestCase = class(TEngineBaseTest)
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protected
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function CreateSolver: ISolver; override;
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published
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procedure TestPart1;
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end;
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{ TLongWalkExampleTestCase }
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TLongWalkExampleTestCase = class(TExampleEngineBaseTest)
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protected
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function CreateSolver: ISolver; override;
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published
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procedure TestPart1;
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end;
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implementation
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{ TLongWalkFullDataTestCase }
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function TLongWalkFullDataTestCase.CreateSolver: ISolver;
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begin
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Result := TLongWalk.Create;
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end;
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procedure TLongWalkFullDataTestCase.TestPart1;
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begin
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AssertEquals(2218, FSolver.GetResultPart1);
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end;
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{ TLongWalkExampleTestCase }
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function TLongWalkExampleTestCase.CreateSolver: ISolver;
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begin
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Result := TLongWalk.Create;
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end;
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procedure TLongWalkExampleTestCase.TestPart1;
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begin
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AssertEquals(94, FSolver.GetResultPart1);
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end;
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initialization
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RegisterTest(TLongWalkFullDataTestCase);
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RegisterTest(TLongWalkExampleTestCase);
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end.
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