Added solution for "Day 18: Lavaduct Lagoon", part 1
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@ -1,6 +1,6 @@
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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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Copyright (C) 2024 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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@ -22,14 +22,35 @@ unit ULavaductLagoon;
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interface
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uses
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Classes, SysUtils, USolver;
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Classes, SysUtils, Generics.Collections, USolver, UCommon;
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type
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{ TDig }
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TDig = record
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Direction: TPoint;
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Length: Cardinal;
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end;
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TDigs = specialize TList<TDig>;
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{ TLavaductLagoon }
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TLavaductLagoon = class(TSolver)
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FDigs: TDigs;
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FCurrentPosiiton: TPoint;
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FDigRect: TRect;
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FDigSite: array of array of Boolean;
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FHigh: TPoint;
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function AddDig(const ALine: string): TDig;
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procedure UpdateDigRect(constref ADig: TDig);
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procedure CalculateDigSite;
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function CalculateLagoonSize: Int64;
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function CheckPositionUntouched(const AX, AY: Integer; var ACount: Integer): Boolean;
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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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@ -40,14 +61,152 @@ implementation
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{ TLavaductLagoon }
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procedure TLavaductLagoon.ProcessDataLine(const ALine: string);
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function TLavaductLagoon.AddDig(const ALine: string): TDig;
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var
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split: TStringArray;
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begin
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split := ALine.Split([' ']);
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case split[0] of
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'R': Result.Direction := CDirectionRight;
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'D': Result.Direction := CDirectionDown;
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'L': Result.Direction := CDirectionLeft;
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'U': Result.Direction := CDirectionUp;
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end;
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Result.Length := StrToUInt(split[1]);
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FDigs.Add(Result);
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end;
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procedure TLavaductLagoon.UpdateDigRect(constref ADig: TDig);
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begin
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if ADig.Direction.Y = 0 then
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begin
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Inc(FCurrentPosiiton.X, ADig.Length * ADig.Direction.X);
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if FCurrentPosiiton.X < FDigRect.Left then
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FDigRect.Left := FCurrentPosiiton.X;
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if FDigRect.Right < FCurrentPosiiton.X then
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FDigRect.Right := FCurrentPosiiton.X;
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end
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else begin
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Inc(FCurrentPosiiton.Y, ADig.Length * ADig.Direction.Y);
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if FCurrentPosiiton.Y < FDigRect.Top then
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FDigRect.Top := FCurrentPosiiton.Y;
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if FDigRect.Bottom < FCurrentPosiiton.Y then
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FDigRect.Bottom := FCurrentPosiiton.Y;
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end;
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end;
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procedure TLavaductLagoon.CalculateDigSite;
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var
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i, j: Integer;
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dig: TDig;
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begin
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// Initializes dig site array.
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FHigh := FDigRect.BottomRight - FDigRect.TopLeft;
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SetLength(FDigSite, FHigh.X + 1, FHigh.Y + 1);
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for i := 0 to FHigh.X do
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for j := 0 to FHigh.Y do
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FDigSite[i, j] := False;
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// Initializes start position.
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FCurrentPosiiton := Point(-FDigRect.Left, -FDigRect.Top);
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FDigSite[FCurrentPosiiton.X, FCurrentPosiiton.Y] := True;
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// Applies digs to dig site array.
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for dig in FDigs do
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for i := 1 to dig.Length do
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begin
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FCurrentPosiiton := FCurrentPosiiton + dig.Direction;
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FDigSite[FCurrentPosiiton.X, FCurrentPosiiton.Y] := True;
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end;
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end;
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function TLavaductLagoon.CalculateLagoonSize: Int64;
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var
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stack: specialize TStack<TPoint>;
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exteriors, i: Integer;
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position, neighbor: TPoint;
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direction: PPoint;
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begin
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// Counts exterior, untouched positions.
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stack := specialize TStack<TPoint>.Create;
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exteriors := 0;
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// Counts untouched position on the edge of the dig site and their neighbors, and pushes those neighbors on the stack.
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// With this we ensure that items on the stack are never on the edge, thus avoiding bounds checks later.
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for i := 0 to FHigh.Y do
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begin
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if CheckPositionUntouched(0, i, exteriors)
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and (1 < i) and (i < FHigh.Y)
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and CheckPositionUntouched(1, i, exteriors) then
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stack.Push(Point(1, i));
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if CheckPositionUntouched(FHigh.X, i, exteriors)
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and (0 < i) and (i < FHigh.Y - 1)
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and CheckPositionUntouched(FHigh.X - 1, i, exteriors) then
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stack.Push(Point(FHigh.X - 1, i));
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end;
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for i := 0 to FHigh.X do
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begin
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if CheckPositionUntouched(i, 0, exteriors)
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and (0 < i) and (i < FHigh.X - 1)
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and CheckPositionUntouched(i, 1, exteriors) then
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stack.Push(Point(i, 1));
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if CheckPositionUntouched(i, FHigh.Y, exteriors)
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and (1 < i) and (i < FHigh.X)
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and CheckPositionUntouched(i, FHigh.Y - 1, exteriors) then
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stack.Push(Point(i, FHigh.Y - 1));
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end;
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// Counts the remaining exterior area while flood-filling the positions.
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while stack.Count > 0 do
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begin
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position := stack.Pop;
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for direction in CPCardinalDirections do
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begin
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neighbor := position + direction^;
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if CheckPositionUntouched(neighbor.X, neighbor.Y, exteriors) then
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stack.Push(neighbor);
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end;
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end;
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stack.Free;
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Result := (FHigh.X + 1) * (FHigh.Y + 1) - exteriors;
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end;
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function TLavaductLagoon.CheckPositionUntouched(const AX, AY: Integer; var ACount: Integer): Boolean;
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begin
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Result := not FDigSite[AX, AY];
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if Result then
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begin
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FDigSite[AX, AY] := True;
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Inc(ACount);
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end;
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end;
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constructor TLavaductLagoon.Create;
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begin
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FDigs := TDigs.Create;
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FCurrentPosiiton := Point(0, 0);
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FDigRect := Rect(0, 0, 0, 0);
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end;
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destructor TLavaductLagoon.Destroy;
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begin
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FDigs.Free;
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inherited Destroy;
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end;
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procedure TLavaductLagoon.ProcessDataLine(const ALine: string);
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var
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dig: TDig;
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begin
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dig := AddDig(ALine);
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UpdateDigRect(dig);
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end;
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procedure TLavaductLagoon.Finish;
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begin
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CalculateDigSite;
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FPart1 := CalculateLagoonSize;
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end;
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function TLavaductLagoon.GetDataFileName: string;
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@ -33,7 +33,7 @@ type
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function CreateSolver: ISolver; override;
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published
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procedure TestPart1;
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procedure TestPart2;
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//procedure TestPart2;
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end;
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implementation
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@ -50,13 +50,13 @@ begin
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AssertEquals(62, FSolver.GetResultPart1);
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end;
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procedure TLavaductLagoonExampleTestCase.TestPart2;
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begin
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AssertEquals(-1, FSolver.GetResultPart2);
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end;
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//procedure TLavaductLagoonExampleTestCase.TestPart2;
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//begin
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// AssertEquals(-1, FSolver.GetResultPart2);
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//end;
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initialization
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//RegisterTest('TLavaductLagoon', TLavaductLagoonExampleTestCase);
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RegisterTest('TLavaductLagoon', TLavaductLagoonExampleTestCase);
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end.
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