Added solution for "Day 9: Mirage Maintenance", part 1

solvers/UMirageMaintenance.pas

@@ -0,0 +1,136 @@
+{
+  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 UMirageMaintenance;
+
+{$mode ObjFPC}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, Generics.Collections, USolver;
+
+type
+
+  { TMirageMaintenance }
+
+  TMirageMaintenance = class(TSolver)
+  private
+    FN: Integer;
+    FLagrangePolynomialsInN: specialize TList<Int64>;
+    procedure CalcLagrangePolynomials;
+  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
+
+{ TMirageMaintenance }
+
+procedure TMirageMaintenance.CalcLagrangePolynomials;
+var
+  sign, i, j: Integer;
+begin
+  FLagrangePolynomialsInN.Clear;
+  if FN mod 2 = 0 then
+    sign := -1
+  else
+    sign := 1;
+
+  // Calculates the polynomials in N and -1.
+  for i := 0 to FN - 1 do
+  begin
+    FLagrangePolynomialsInN.Add(sign);
+    sign := -sign;
+
+    if i < FN - FN div 2 then
+    begin
+      // Multiplies by the non-cancelled numerator terms.
+      for j := FN - i + 1 to FN do
+        FLagrangePolynomialsInN[i] := FLagrangePolynomialsInN[i] * j;
+      // Divides by the non-cancelled denominator terms.
+      for j := 2 to i do
+        FLagrangePolynomialsInN[i] := FLagrangePolynomialsInN[i] div j;
+    end
+    else begin
+      // Multiplies by the non-cancelled numerator terms.
+      for j := i + 1 to FN do
+        FLagrangePolynomialsInN[i] := FLagrangePolynomialsInN[i] * j;
+      // Divides by the non-cancelled over-counted numerator term.
+      FLagrangePolynomialsInN[i] := FLagrangePolynomialsInN[i] div (FN - i);
+      // Divides by the non-cancelled denominator terms.
+      for j := 2 to FN - i - 1 do
+        FLagrangePolynomialsInN[i] := FLagrangePolynomialsInN[i] div j;
+    end;
+  end;
+end;
+
+constructor TMirageMaintenance.Create;
+begin
+  FLagrangePolynomialsInN := specialize TList<Int64>.Create;
+  FN := 0;
+end;
+
+destructor TMirageMaintenance.Destroy;
+begin
+  FLagrangePolynomialsInN.Free;
+  inherited Destroy;
+end;
+
+procedure TMirageMaintenance.ProcessDataLine(const ALine: string);
+var
+  split: TStringArray;
+  i, y: Integer;
+  p: Int64;
+begin
+  split := ALine.Split(' ');
+  if Length(split) <> FN then
+  begin
+    FN := Length(split);
+    CalcLagrangePolynomials;
+  end;
+
+  for i := 0 to FN - 1 do
+  begin
+    y := StrToInt(split[i]);
+    p := y * FLagrangePolynomialsInN[i];
+    Inc(FPart1, p);
+  end;
+end;
+
+procedure TMirageMaintenance.Finish;
+begin
+
+end;
+
+function TMirageMaintenance.GetDataFileName: string;
+begin
+  Result := 'mirage_maintenance.txt';
+end;
+
+function TMirageMaintenance.GetPuzzleName: string;
+begin
+  Result := 'Day 9: Mirage Maintenance';
+end;
+
+end.
+