AdventOfCode2023/solvers/UCosmicExpansion.pas

{
  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 UCosmicExpansion;

{$mode ObjFPC}{$H+}

interface

uses
  Classes, SysUtils, Generics.Collections, Math, USolver;

const
  CGalaxyChar = '#';
  CEmptySpaceFactor = 2;
  CNonEmptySpaceFactor = 1;

type

  { TCosmicExpansion }

  TCosmicExpansion = class(TSolver)
  private
    FColumnExpansion, FRowExpansion: specialize TList<Integer>;
    FGalaxies: specialize TList<TPoint>;
    procedure InitColumnExpansion(const ASize: Integer);
  public
    constructor Create;
    destructor Destroy; override;
    procedure ProcessDataLine(const ALine: string); override;
    procedure Finish; override;
    function GetDataFileName: string; override;
    function GetPuzzleName: string; override;
  end;

implementation

{ TCosmicExpansion }

procedure TCosmicExpansion.InitColumnExpansion(const ASize: Integer);
var
  i: Integer;
begin
  if FColumnExpansion.Count = 0 then
  begin
    FColumnExpansion.Capacity := ASize;
    for i := 1 to ASize do
      FColumnExpansion.Add(CEmptySpaceFactor);
  end;
end;

constructor TCosmicExpansion.Create;
begin
  FColumnExpansion := specialize TList<Integer>.Create;
  FRowExpansion := specialize TList<Integer>.Create;
  FGalaxies := specialize TList<TPoint>.Create;
end;

destructor TCosmicExpansion.Destroy;
begin
  FColumnExpansion.Free;
  FRowExpansion.Free;
  FGalaxies.Free;
  inherited Destroy;
end;

procedure TCosmicExpansion.ProcessDataLine(const ALine: string);
var
  empty: Boolean;
  i : Integer;
begin
  InitColumnExpansion(Length(ALine));

  empty := True;
  for i := 1 to Length(ALine) do
    if ALine[i] = CGalaxyChar then
    begin
      FGalaxies.Add(Point(i, FRowExpansion.Count));
      empty := False;
      FColumnExpansion[i - 1] := CNonEmptySpaceFactor;
    end;

  if empty then
    FRowExpansion.Add(CEmptySpaceFactor)
  else
    FRowExpansion.Add(CNonEmptySpaceFactor);
end;

procedure TCosmicExpansion.Finish;
var
  i, j, k: Integer;
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]);
      for k := Min(FGalaxies[i].Y, FGalaxies[j].Y) + 1 to Max(FGalaxies[i].Y, FGalaxies[j].Y) do
        Inc(FPart1, FRowExpansion[k]);
    end;
end;

function TCosmicExpansion.GetDataFileName: string;
begin
  Result := 'cosmic_expansion.txt';
end;

function TCosmicExpansion.GetPuzzleName: string;
begin
   Result := 'Day 11: Cosmic Expansion';
end;

end.