Added solution for "Day 3: Gear Ratios", part 2

solvers/UGearRatios.pas

@@ -22,21 +22,59 @@ unit UGearRatios;
 interface
 
 uses
-  Classes, SysUtils, USolver;
+  Classes, SysUtils, fgl, USolver;
 
 const
   CDigitChars = ['0'..'9'];
   CNonSymbolChars = ['0'..'9', '.'];
+  CGearChar = '*';
 
 type
 
+  { TGearCandidate }
+
+  TGearCandidate = class
+  private
+    FColumn, FPartNumber1, FPartNumber2, FPartNumber3: Integer;
+  public
+    constructor Create(AColumn: Integer);
+    procedure AddPartNumber(APartNumber: Integer);
+    function GetGearRatio: Integer;
+    property Column: Integer read FColumn;
+  end;
+
+  { TGearCandidates }
+
+  TGearCandidates = specialize TFPGObjectList<TGearCandidate>;
+
+  { TGearCandidateTracker }
+
+  TGearCandidateTracker = class
+  private
+    FPreviousLine, FLine, FNextLine, FCurrentNumber: TGearCandidates;
+  public
+    constructor Create;
+    destructor Destroy; override;
+    function GetLine(AIndex: Integer): TGearCandidates;
+    function FinishLine: Integer;
+    property PreviousLine: TGearCandidates read FPreviousLine;
+    property Line: TGearCandidates read FLine;
+    property NextLine: TGearCandidates read FNextLine;
+    property CurrentNumber: TGearCandidates read FCurrentNumber;
+  end;
+
   { TGearRatios }
 
   TGearRatios = class(TSolver)
   private
     FPreviousLine, FLine: string;
+    FGearTracker: TGearCandidateTracker;
     procedure ProcessDataLineTriplet(const APreviousLine, ALine, ANextLine: string);
+    function HasSymbolCharInColumn(const AIndex: Integer; const ALines: array of string): Boolean;
+    procedure LogForCurrentGearCandidates(const APartNumber: Integer);
   public
+    constructor Create;
+    destructor Destroy; override;
     procedure ProcessDataLine(const ALine: string); override;
     procedure Finish; override;
     function GetDataFileName: string; override;
@@ -45,6 +83,80 @@ type
 
 implementation
 
+{ TGearCandidate }
+
+constructor TGearCandidate.Create(AColumn: Integer);
+begin
+  FColumn := AColumn;
+  FPartNumber1 := 0;
+  FPartNumber2 := 0;
+  FPartNumber3 := 0;
+end;
+
+procedure TGearCandidate.AddPartNumber(APartNumber: Integer);
+begin
+  if FPartNumber1 = 0 then
+    FPartNumber1 := APartNumber
+  else if FPartNumber2 = 0 then
+    FPartNumber2 := APartNumber
+  else
+    FPartNumber3 := APartNumber;
+end;
+
+function TGearCandidate.GetGearRatio: Integer;
+begin
+  if FPartNumber3 = 0 then
+    Result := FPartNumber1 * FPartNumber2
+  else
+    Result := 0;
+end;
+
+{ TGearCandidateTracker }
+
+constructor TGearCandidateTracker.Create;
+begin
+  FPreviousLine := TGearCandidates.Create;
+  FLine := TGearCandidates.Create;
+  FNextLine := TGearCandidates.Create;
+  FCurrentNumber := TGearCandidates.Create(False);
+end;
+
+destructor TGearCandidateTracker.Destroy;
+begin
+  FPreviousLine.Free;
+  FLine.Free;
+  FNextLine.Free;
+  FCurrentNumber.Free;
+  inherited Destroy;
+end;
+
+function TGearCandidateTracker.GetLine(AIndex: Integer): TGearCandidates;
+begin
+  case AIndex of
+    0: Result := FPreviousLine;
+    1: Result := FLine;
+    2: Result := FNextLine;
+    else Result := nil;
+  end;
+end;
+
+function TGearCandidateTracker.FinishLine: Integer;
+var
+  candidate: TGearCandidate;
+  temp: TGearCandidates;
+begin
+  Result := 0;
+  for candidate in FPreviousLine do
+  begin
+    Inc(Result, candidate.GetGearRatio);
+  end;
+  FPreviousLine.Clear;
+  temp := FPreviousLine;
+  FPreviousLine := FLine;
+  FLine := FNextLine;
+  FNextLine := temp;
+end;
+
 { TGearRatios }
 
 procedure TGearRatios.ProcessDataLineTriplet(const APreviousLine, ALine, ANextLine: string);
@@ -61,35 +173,21 @@ begin
     begin
       inNumber := True;
       numberStart := i;
+      FGearTracker.CurrentNumber.Clear;
 
       // Checks for a symbol in the column before the first digit.
-      isPartNumber := (i > 1) and
+      isPartNumber := (i > 1) and HasSymbolCharInColumn(i - 1, [APreviousLine, ALine, ANextLine]);
-        (not (APreviousLine[i - 1] in CNonSymbolChars)
-        or not (ALine[i - 1] in CNonSymbolChars)
-        or not (ANextLine[i - 1] in CNonSymbolChars));
     end;
 
     // Checks for a symbol in the column of the current digit.
-    if inNumber and not isPartNumber and
+    if inNumber and HasSymbolCharInColumn(i, [APreviousLine, ALine, ANextLine]) then
-      (not (APreviousLine[i] in CNonSymbolChars)
-      or not (ANextLine[i] in CNonSymbolChars)) then
-    begin
       isPartNumber := True;
-    end;
 
     // Checks if number ends.
     if inNumber and (not (ALine[i] in CDigitChars) or (i = ALine.Length)) then
     begin
       inNumber := False;
 
-      // Checks for a symbol in the column after the last digit.
-      if not (APreviousLine[i] in CNonSymbolChars)
-        or not (ALine[i] in CNonSymbolChars)
-        or not (ANextLine[i] in CNonSymbolChars) then
-      begin
-        isPartNumber := True;
-      end;
-
       // Counts if it is a part number.
       if isPartNumber then
       begin
@@ -98,9 +196,71 @@ begin
           Inc(numberLength);
         partNumber := StrToInt(Copy(ALine, numberStart, numberLength));
         Inc(FPart1, partNumber);
+        LogForCurrentGearCandidates(partNumber);
       end;
     end;
   end;
+
+  Inc(FPart2, FGearTracker.FinishLine);
+end;
+
+function TGearRatios.HasSymbolCharInColumn(const AIndex: Integer; const ALines: array of string): Boolean;
+var
+  i: Integer;
+  candidates: TGearCandidates;
+  candidate: TGearCandidate;
+  exists: Boolean;
+begin
+  Result := False;
+  for i := 0 to High(ALines) do
+    if not (ALines[i][AIndex] in CNonSymbolChars) then
+    begin
+      Result := True;
+      // Could exit here for part 1, the following is only for part 2.
+      if ALines[i][AIndex] = CGearChar then
+      begin
+        candidates := FGearTracker.GetLine(i);
+        exists := False;
+        for candidate in candidates do
+        begin
+          if candidate.Column = AIndex then
+          begin
+            // The current gear candidate has already been found.
+            FGearTracker.CurrentNumber.Add(candidate);
+            exists := True;
+            Break;
+          end;
+        end;
+        if not exists then
+        begin
+          // A new gear candidate was found.
+          candidate := TGearCandidate.Create(AIndex);
+          candidates.Add(candidate);
+          FGearTracker.CurrentNumber.Add(candidate);
+        end;
+      end;
+    end;
+end;
+
+procedure TGearRatios.LogForCurrentGearCandidates(const APartNumber: Integer);
+var
+  candidate: TGearCandidate;
+begin
+  for candidate in FGearTracker.CurrentNumber do
+  begin
+    candidate.AddPartNumber(APartNumber);
+  end;
+end;
+
+constructor TGearRatios.Create;
+begin
+  FGearTracker := TGearCandidateTracker.Create;
+end;
+
+destructor TGearRatios.Destroy;
+begin
+  FGearTracker.Free;
+  inherited Destroy;
 end;
 
 procedure TGearRatios.ProcessDataLine(const ALine: string);

tests/UGearRatiosTestCases.pas

@@ -44,6 +44,7 @@ type
     procedure TearDown; override;
   published
     procedure TestPart1;
+    procedure TestPart2;
   end;
 
   { TGearRatiosTestCase }
@@ -97,6 +98,12 @@ begin
   AssertEquals(530495, FSolver.GetResultPart1);
 end;
 
+procedure TGearRatiosFullDataTestCase.TestPart2;
+begin
+  AssertEquals(80253814, FSolver.GetResultPart2);
+end;
+
+
 { TGearRatiosTestCase }
 
 procedure TGearRatiosTestCase.TestEndOfLineNumber;

tests/bin/AdventOfCodeFPCUnit.fpcunit.ini

@@ -11,6 +11,8 @@ TGearRatiosFullDataTestCase.Checked=1
 TGearRatiosFullDataTestCase.Expanded=1
 TGearRatiosFullDataTestCase.TestPart1.Checked=1
 TGearRatiosFullDataTestCase.TestPart1.Expanded=0
+TGearRatiosFullDataTestCase.TestPart2.Checked=1
+TGearRatiosFullDataTestCase.TestPart2.Expanded=0
 TGearRatiosTestCase.Checked=1
 TGearRatiosTestCase.Expanded=1
 TGearRatiosTestCase.TestEndOfLineNumber.Checked=1