Added solution for "Day 23: A Long Walk", part 1

This commit is contained in:
Stefan Müller 2023-12-25 00:44:13 +01:00 committed by Stefan Müller
parent c3ecaf59fa
commit 5495b32692
6 changed files with 410 additions and 2 deletions

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@ -129,6 +129,10 @@
<Filename Value="solvers\USandSlabs.pas"/>
<IsPartOfProject Value="True"/>
</Unit>
<Unit>
<Filename Value="solvers\ULongWalk.pas"/>
<IsPartOfProject Value="True"/>
</Unit>
</Units>
</ProjectOptions>
<CompilerOptions>

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@ -27,7 +27,7 @@ uses
UTrebuchet, UCubeConundrum, UGearRatios, UScratchcards, UGiveSeedFertilizer, UWaitForIt, UCamelCards,
UHauntedWasteland, UNumberTheory, UMirageMaintenance, UPipeMaze, UCosmicExpansion, UHotSprings, UPointOfIncidence,
UParabolicReflectorDish, ULensLibrary, UFloorWillBeLava, UClumsyCrucible, ULavaductLagoon, UAplenty,
UPulsePropagation, UStepCounter, USandSlabs;
UPulsePropagation, UStepCounter, USandSlabs, ULongWalk;
type
@ -91,6 +91,7 @@ begin
20: engine.RunAndFree(TPulsePropagation.Create);
21: engine.RunAndFree(TStepCounter.Create);
22: engine.RunAndFree(TSandSlabs.Create);
23: engine.RunAndFree(TLongWalk.Create);
end;
engine.Free;

321
solvers/ULongWalk.pas Normal file
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@ -0,0 +1,321 @@
{
Solutions to the Advent Of Code.
Copyright (C) 2023 Stefan Müller
This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
}
unit ULongWalk;
{$mode ObjFPC}{$H+}
interface
uses
Classes, SysUtils, Generics.Collections, USolver;
type
TPoints = specialize TList<TPoint>;
TCrossing = class;
{ TPath }
TPath = class
private
FEnd: TCrossing;
FLength: Integer;
public
property EndCrossing: TCrossing read FEnd;
property Length: Integer read FLength;
constructor Create(const ALength: Integer; const AEnd: TCrossing);
end;
TPaths = specialize TObjectList<TPath>;
{ TPathStart }
TPathStart = record
Position, ReverseDirection: TPoint;
Crossing: TCrossing;
end;
TPathStartQueue = specialize TQueue<TPathStart>;
{ TCrossing }
TCrossing = class
private
FPosition: TPoint;
FOutPaths: TPaths;
FDistance: Integer;
public
property Position: TPoint read FPosition;
property OutPaths: TPaths read FOutPaths;
property Distance: Integer read FDistance write FDistance;
constructor Create(constref APosition: TPoint);
destructor Destroy; override;
procedure AddOutPath(const AOutPath: TPath);
end;
TCrossings = specialize TObjectList<TCrossing>;
TCrossingStack = specialize TStack<TCrossing>;
{ TLongWalk }
TLongWalk = class(TSolver)
private
FLines: TStringList;
FPaths: TPaths;
FCrossings, FWaitingForOtherInPath: TCrossings;
FStart: TCrossing;
function GetPosition(constref APoint: TPoint): Char;
procedure ProcessPaths;
procedure StepPath(const AStartPositionQueue: TPathStartQueue);
function FindOrCreateCrossing(constref APosition: TPoint; const AStartPositionQueue: TPathStartQueue): TCrossing;
procedure FindLongestPath;
public
constructor Create;
destructor Destroy; override;
procedure ProcessDataLine(const ALine: string); override;
procedure Finish; override;
function GetDataFileName: string; override;
function GetPuzzleName: string; override;
end;
TDirection = (dirRight, dirDown, dirLeft, dirUp);
const
CPathChar = '.';
CForestChar = '#';
CRightSlopeChar = '>';
CDownSlopeChar = 'v';
CDirections: array[TDirection] of TPoint = ((X: 1; Y: 0), (X: 0; Y: 1), (X: -1; Y: 0), (X: 0; Y: -1));
CStartReverseDirection: TPoint = (X: 0; Y: -1);
implementation
{ TPath }
constructor TPath.Create(const ALength: Integer; const AEnd: TCrossing);
begin
FLength := ALength;
FEnd := AEnd;
end;
{ TCrossing }
constructor TCrossing.Create(constref APosition: TPoint);
begin
FPosition := APosition;
FOutPaths := TPaths.Create(False);
FDistance := 0;
end;
destructor TCrossing.Destroy;
begin
FOutPaths.Free;
inherited Destroy;
end;
procedure TCrossing.AddOutPath(const AOutPath: TPath);
begin
FOutPaths.Add(AOutPath);
end;
{ TLongWalk }
function TLongWalk.GetPosition(constref APoint: TPoint): Char;
begin
Result := FLines[APoint.Y][APoint.X];
end;
procedure TLongWalk.ProcessPaths;
var
stack: TPathStartQueue;
pathStart: TPathStart;
begin
stack := TPathStartQueue.Create;
pathStart.Position := FStart.Position;
pathStart.Crossing := FStart;
pathStart.ReverseDirection := CStartReverseDirection;
stack.Enqueue(pathStart);
while stack.Count > 0 do
StepPath(stack);
stack.Free;
end;
procedure TLongWalk.StepPath(const AStartPositionQueue: TPathStartQueue);
var
start: TPathStart;
new, direction: TPoint;
c: Char;
len: Integer;
oneMore, stop: Boolean;
crossing: TCrossing;
path: TPath;
begin
start := AStartPositionQueue.Dequeue;
len := 1;
if start.Crossing <> FStart then
Inc(len);
oneMore := False;
stop := False;
repeat
for direction in CDirections do
if direction <> start.ReverseDirection then
begin
new := start.Position + direction;
c := GetPosition(new);
if c <> CForestChar then
begin
start.ReverseDirection := Point(-direction.X, -direction.Y);
start.Position := new;
if oneMore or (new.Y = FLines.Count - 1) then
stop := True
else
Inc(len);
if c <> CPathChar then
oneMore := True;
Break;
end;
end;
until stop;
crossing := FindOrCreateCrossing(start.Position, AStartPositionQueue);
path := TPath.Create(len, crossing);
FPaths.Add(path);
start.Crossing.AddOutPath(path);
end;
// Crossing with multiple (two) entries will only be added to FCrossings once both in-paths have been processed. This
// guarantees a topological order in the list of crossings, which is required for our longest path algorithm.
function TLongWalk.FindOrCreateCrossing(constref APosition: TPoint; const AStartPositionQueue: TPathStartQueue):
TCrossing;
var
i: Integer;
pathStart: TPathStart;
begin
Result := nil;
// Checks if the crossing has already been encountered.
i := 0;
while (i < FWaitingForOtherInPath.Count) and (Result = nil) do
begin
if FWaitingForOtherInPath[i].Position = APosition then
begin
Result := FWaitingForOtherInPath[i];
FCrossings.Add(Result);
end
else
Inc(i);
end;
if Result <> nil then
begin
FWaitingForOtherInPath.Delete(i);
Exit;
end;
// Creates a new crossing.
Result := TCrossing.Create(APosition);
// Checks if the new crossing has multiple entries.
if (GetPosition(APosition + CDirections[dirLeft]) = CRightSlopeChar)
and (GetPosition(APosition + CDirections[dirUp]) = CDownSlopeChar) then
FWaitingForOtherInPath.Add(Result)
else
FCrossings.Add(Result);
if APosition.Y < FLines.Count - 1 then
begin
// Adds the exits of this crossing to the stack as starts for new paths.
pathStart.Crossing := Result;
pathStart.Position := APosition + CDirections[dirRight];
if GetPosition(pathStart.Position) = CRightSlopeChar then
begin
pathStart.ReverseDirection := CDirections[dirLeft];
AStartPositionQueue.Enqueue(pathStart);
end;
pathStart.Position := APosition + CDirections[dirDown];
if GetPosition(pathStart.Position) = CDownSlopeChar then
begin
pathStart.ReverseDirection := CDirections[dirUp];
AStartPositionQueue.Enqueue(pathStart);
end;
end
end;
procedure TLongWalk.FindLongestPath;
var
crossing: TCrossing;
path: TPath;
begin
for crossing in FCrossings do
begin
for path in crossing.OutPaths do
if path.EndCrossing.Distance < crossing.Distance + path.Length then
path.EndCrossing.Distance := crossing.Distance + path.Length;
end;
FPart1 := FCrossings.Last.Distance;
end;
constructor TLongWalk.Create;
begin
FLines := TStringList.Create;
FPaths := TPaths.Create;
FCrossings := TCrossings.Create;
FWaitingForOtherInPath := TCrossings.Create(False);
end;
destructor TLongWalk.Destroy;
begin
FLines.Free;
FPaths.Free;
FCrossings.Free;
FWaitingForOtherInPath.Free;
inherited Destroy;
end;
procedure TLongWalk.ProcessDataLine(const ALine: string);
begin
if FLines.Count = 0 then
begin
FStart := TCrossing.Create(Point(ALine.IndexOf(CPathChar) + 1, 0));
FCrossings.Add(FStart);
end;
FLines.Add(ALine);
end;
procedure TLongWalk.Finish;
begin
ProcessPaths;
FindLongestPath;
end;
function TLongWalk.GetDataFileName: string;
begin
Result := 'long_walk.txt';
end;
function TLongWalk.GetPuzzleName: string;
begin
Result := 'Day 23: A Long Walk';
end;
end.

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@ -132,6 +132,10 @@
<Filename Value="USandSlabsTestCases.pas"/>
<IsPartOfProject Value="True"/>
</Unit>
<Unit>
<Filename Value="ULongWalkTestCases.pas"/>
<IsPartOfProject Value="True"/>
</Unit>
</Units>
</ProjectOptions>
<CompilerOptions>

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@ -8,7 +8,7 @@ uses
UHauntedWastelandTestCases, UMirageMaintenanceTestCases, UPipeMazeTestCases, UCosmicExpansionTestCases,
UHotSpringsTestCases, UPointOfIncidenceTestCases, UParabolicReflectorDishTestCases, ULensLibraryTestCases,
UFloorWillBeLavaTestCases, UClumsyCrucibleTestCases, ULavaductLagoonTestCases, UAplentyTestCases,
UPulsePropagationTestCases, UStepCounterTestCases, USandSlabsTestCases;
UPulsePropagationTestCases, UStepCounterTestCases, USandSlabsTestCases, ULongWalkTestCases;
{$R *.res}

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@ -0,0 +1,78 @@
{
Solutions to the Advent Of Code.
Copyright (C) 2023 Stefan Müller
This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
}
unit ULongWalkTestCases;
{$mode ObjFPC}{$H+}
interface
uses
Classes, SysUtils, fpcunit, testregistry, USolver, UBaseTestCases, ULongWalk;
type
{ TLongWalkFullDataTestCase }
TLongWalkFullDataTestCase = class(TEngineBaseTest)
protected
function CreateSolver: ISolver; override;
published
procedure TestPart1;
end;
{ TLongWalkExampleTestCase }
TLongWalkExampleTestCase = class(TExampleEngineBaseTest)
protected
function CreateSolver: ISolver; override;
published
procedure TestPart1;
end;
implementation
{ TLongWalkFullDataTestCase }
function TLongWalkFullDataTestCase.CreateSolver: ISolver;
begin
Result := TLongWalk.Create;
end;
procedure TLongWalkFullDataTestCase.TestPart1;
begin
AssertEquals(2218, FSolver.GetResultPart1);
end;
{ TLongWalkExampleTestCase }
function TLongWalkExampleTestCase.CreateSolver: ISolver;
begin
Result := TLongWalk.Create;
end;
procedure TLongWalkExampleTestCase.TestPart1;
begin
AssertEquals(94, FSolver.GetResultPart1);
end;
initialization
RegisterTest(TLongWalkFullDataTestCase);
RegisterTest(TLongWalkExampleTestCase);
end.