Added solution for "Day 17: Clumsy Crucible", part 2

solvers/UClumsyCrucible.pas

@@ -22,7 +22,7 @@ unit UClumsyCrucible;
 interface
 
 uses
-  Classes, SysUtils, Generics.Collections, Math, USolver;
+  Classes, SysUtils, Generics.Collections, Math, USolver, UCommon;
 
 type
 
@@ -39,27 +39,58 @@ type
     NeedsUpdate: Boolean;
   end;
 
+  TAxisId = (axHorizontal, axVertical);
+
+const
+  CAxisDirections: array[TAxisId] of array[0..1] of PPoint
+    = ((@CDirectionRight, @CDirectionLeft), (@CDirectionDown, @CDirectionUp));
+  COtherAxes: array[TAxisId] of TAxisId = (axVertical, axHorizontal);
+
+type
   { TNode }
 
   TNode = record
-    Horizontal, Vertical: TAxisData;
+    Axes: array[TAxisId] of TAxisData;
     LocalHeatLoss: Byte;
   end;
+  PNode = ^TNode;
 
   TNodeArray = array of TNode;
   TNodeArrays = specialize TList<TNodeArray>;
 
   TWorkQueue = specialize TQueue<TPoint>;
 
+  { TNodeMap }
+
+  TNodeMap = class
+  private
+    // Each item in FNodes is a horizontal row of nodes.
+    FNodes: TNodeArrays;
+    FWidth: Integer;
+    FMinStraight, FMaxStraight: Integer;
+    function GetHeight: Integer;
+    function GetNode(APosition: TPoint): TNode;
+    function GetPNode(APosition: TPoint): PNode;
+    function IsPositionInMap(constref APosition: TPoint): Boolean;
+    procedure ClampPositionToMap(var APosition: TPoint);
+    procedure InitWorkQueue(constref AWorkQueue: TWorkQueue);
+    procedure InvalidateNeighbors(constref AWorkQueue: TWorkQueue; const AAxis: TAxisId; constref APosition: TPoint);
+    function FindStepNodeMinimum(const AAxis: TAxisId; constref APosition: TPoint): Cardinal;
+  public
+    property Width: Integer read FWidth;
+    property Height: Integer read GetHeight;
+    constructor Create;
+    destructor Destroy; override;
+    procedure AddNodes(const ALine: string);
+    function FindMinimumPathLength(const AMinStraight, AMaxStraight: Integer): Cardinal;
+    procedure Reset;
+  end;
+
   { TClumsyCrucible }
 
   TClumsyCrucible = class(TSolver)
   private
-    // Each item in FMap is a horizontal row of nodes.
+    FMap: TNodeMap;
-    FMap: TNodeArrays;
-    FWidth: Integer;
-    procedure InvalidateHorizontalNeighbors(constref APosition: TPoint; constref AWorkQueue: TWorkQueue);
-    procedure InvalidateVerticalNeighbors(constref APosition: TPoint; constref AWorkQueue: TWorkQueue);
   public
     constructor Create;
     destructor Destroy; override;
@@ -72,39 +103,227 @@ type
 implementation
 
 const
+  CMinStraight = 1;
   CMaxStraight = 3;
+  CUltraMinStraight = 4;
+  CUltraMaxStraight = 10;
+
+{ TNodeMap }
+
+function TNodeMap.GetHeight: Integer;
+begin
+  Result := FNodes.Count;
+end;
+
+function TNodeMap.GetNode(APosition: TPoint): TNode;
+begin
+  Result := FNodes[APosition.Y][APosition.X];
+end;
+
+function TNodeMap.GetPNode(APosition: TPoint): PNode;
+begin
+  Result := @FNodes[APosition.Y][APosition.X];
+end;
+
+function TNodeMap.IsPositionInMap(constref APosition: TPoint): Boolean;
+begin
+  Result := (0 <= APosition.X) and (APosition.X < Width) and (0 <= APosition.Y) and (APosition.Y < Height);
+end;
+
+procedure TNodeMap.ClampPositionToMap(var APosition: TPoint);
+begin
+  if APosition.X < -1 then
+    APosition.X := -1
+  else if APosition.X > Width then
+    APosition.X := Width;
+  if APosition.Y < -1 then
+    APosition.Y := -1
+  else if APosition.Y > Height then
+    APosition.Y := Height;
+end;
+
+procedure TNodeMap.InitWorkQueue(constref AWorkQueue: TWorkQueue);
+var
+  position: TPoint;
+  last: PNode;
+  axis: TAxisId;
+begin
+  // Initializes the end node and the work queue with its neighbors.
+  position := Point(Width - 1, Height - 1);
+  last := GetPNode(position);
+  for axis in TAxisId do
+  begin
+    last^.Axes[axis].Minimum := 0;
+    last^.Axes[axis].IsTraversed := True;
+  end;
+  InvalidateNeighbors(AWorkQueue, axHorizontal, position);
+  InvalidateNeighbors(AWorkQueue, axVertical, position);
+end;
+
+procedure TNodeMap.InvalidateNeighbors(constref AWorkQueue: TWorkQueue; const AAxis: TAxisId; constref APosition:
+  TPoint);
+var
+  otherAxis: TAxisId;
+  nodeMinimum: Cardinal;
+  direction: PPoint;
+  neighborPos, stop: TPoint;
+  neighbor: PNode;
+begin
+  otherAxis := COtherAxes[AAxis];
+  nodeMinimum := GetNode(APosition).Axes[otherAxis].Minimum;
+
+  for direction in CAxisDirections[AAxis] do
+  begin
+    neighborPos := Point(APosition.X + direction^.X * FMinStraight, APosition.Y + direction^.Y * FMinStraight);
+    if IsPositionInMap(neighborPos) then
+    begin
+      stop := Point(APosition.X + direction^.X * (FMaxStraight + 1), APosition.Y + direction^.Y * (FMaxStraight + 1));
+      ClampPositionToMap(stop);
+      while neighborPos <> stop do
+      begin
+        neighbor := GetPNode(neighborPos);
+        if not neighbor^.Axes[AAxis].NeedsUpdate
+        and (not neighbor^.Axes[AAxis].IsTraversed or (neighbor^.Axes[AAxis].Minimum > nodeMinimum)) then
+        begin
+          neighbor^.Axes[AAxis].NeedsUpdate := True;
+          if not neighbor^.Axes[otherAxis].NeedsUpdate then
+            AWorkQueue.Enqueue(neighborPos);
+        end;
+        neighborPos := neighborPos + direction^;
+      end;
+    end;
+  end;
+end;
+
+function TNodeMap.FindStepNodeMinimum(const AAxis: TAxisId; constref APosition: TPoint): Cardinal;
+var
+  otherAxis: TAxisId;
+  direction: PPoint;
+  acc: Cardinal;
+  neighborPos, start, stop: TPoint;
+  isStartReached: Boolean;
+  neighbor: TNode;
+begin
+  otherAxis := COtherAxes[AAxis];
+  Result := Cardinal.MaxValue;
+
+  for direction in CAxisDirections[AAxis] do
+  begin
+    acc := 0;
+    isStartReached := False;
+    neighborPos := APosition + direction^;
+    start := Point(APosition.X + direction^.X * FMinStraight, APosition.Y + direction^.Y * FMinStraight);
+    if IsPositionInMap(start) then
+    begin
+      stop := Point(APosition.X + direction^.X * (FMaxStraight + 1), APosition.Y + direction^.Y * (FMaxStraight + 1));
+      ClampPositionToMap(stop);
+      while neighborPos <> stop do
+      begin
+        if neighborPos = start then
+          isStartReached := True;
+        neighbor := GetNode(neighborPos);
+        Inc(acc, neighbor.LocalHeatLoss);
+        if isStartReached and neighbor.Axes[otherAxis].IsTraversed then
+          Result := Min(Result, neighbor.Axes[otherAxis].Minimum + acc);
+        neighborPos := neighborPos + direction^;
+      end;
+    end;
+  end;
+end;
+
+constructor TNodeMap.Create;
+begin
+  FNodes := TNodeArrays.Create;
+end;
+
+destructor TNodeMap.Destroy;
+begin
+  FNodes.Free;
+  inherited Destroy;
+end;
+
+procedure TNodeMap.AddNodes(const ALine: string);
+var
+  i: Integer;
+  nodes: TNodeArray;
+  axis: TAxisId;
+begin
+  FWidth := Length(ALine);
+  SetLength(nodes, FWidth);
+  for i := 0 to FWidth - 1 do
+  begin
+    nodes[i].LocalHeatLoss := StrToInt(ALine[i + 1]);
+    for axis in TAxisId do
+    begin
+      nodes[i].Axes[axis].IsTraversed := False;
+      nodes[i].Axes[axis].NeedsUpdate := False;
+    end;
+  end;
+  FNodes.Add(nodes);
+end;
+
+function TNodeMap.FindMinimumPathLength(const AMinStraight, AMaxStraight: Integer): Cardinal;
+var
+  queue: TWorkQueue;
+  position: TPoint;
+  node: PNode;
+  axis: TAxisId;
+  start: TNode;
+  newMinimum: Cardinal;
+begin
+  FMinStraight := AMinStraight;
+  FMaxStraight := AMaxStraight;
+
+  queue := TWorkQueue.Create;
+  InitWorkQueue(queue);
+
+  // Processes work queue.
+  while queue.Count > 0 do
+  begin
+    position := queue.Dequeue;
+    node := GetPNode(position);
+
+    for axis in TAxisId do
+      if node^.Axes[axis].NeedsUpdate then
+      begin
+        node^.Axes[axis].NeedsUpdate := False;
+        // Finds minimum for one step from this node along this axis.
+        newMinimum := FindStepNodeMinimum(axis, position);
+        if not node^.Axes[axis].IsTraversed or (node^.Axes[axis].Minimum > newMinimum) then
+        begin
+          // Updates this axis minimum and queues update for neighbors on the other axis.
+          node^.Axes[axis].IsTraversed := True;
+          node^.Axes[axis].Minimum := newMinimum;
+          InvalidateNeighbors(queue, COtherAxes[axis], position);
+        end;
+      end;
+  end;
+
+  queue.Free;
+
+  start := GetNode(Point(0, 0));
+  Result := Min(start.Axes[axHorizontal].Minimum, start.Axes[axVertical].Minimum);
+end;
+
+procedure TNodeMap.Reset;
+var
+  i, j: Integer;
+  axis: TAxisId;
+begin
+  for i := 0 to Width - 1 do
+    for j := 0 to Height - 1 do
+      for axis in TAxisId do
+      begin
+        FNodes[j][i].Axes[axis].IsTraversed := False;
+        FNodes[j][i].Axes[axis].NeedsUpdate := False;
+      end;
+end;
 
 { TClumsyCrucible }
 
-procedure TClumsyCrucible.InvalidateHorizontalNeighbors(constref APosition: TPoint; constref AWorkQueue: TWorkQueue);
-var
-  i: Integer;
-begin
-  for i := Min(FWidth - 1, APosition.X + CMaxStraight) downto Max(0, APosition.X - CMaxStraight) do
-    if (i <> APosition.X) and not FMap[APosition.Y][i].Horizontal.NeedsUpdate then
-    begin
-      FMap[APosition.Y][i].Horizontal.NeedsUpdate := True;
-      if not FMap[APosition.Y][i].Vertical.NeedsUpdate then
-        AWorkQueue.Enqueue(Point(i, APosition.Y));
-    end;
-end;
-
-procedure TClumsyCrucible.InvalidateVerticalNeighbors(constref APosition: TPoint; constref AWorkQueue: TWorkQueue);
-var
-  i: Integer;
-begin
-  for i := Min(FMap.Count - 1, APosition.Y + CMaxStraight) downto Max(0, APosition.Y - CMaxStraight) do
-    if (i <> APosition.Y) and not FMap[i][APosition.X].Vertical.NeedsUpdate then
-    begin
-      FMap[i][APosition.X].Vertical.NeedsUpdate := True;
-      if not FMap[i][APosition.X].Horizontal.NeedsUpdate then
-        AWorkQueue.Enqueue(Point(APosition.X, i));
-    end;
-end;
-
 constructor TClumsyCrucible.Create;
 begin
-  FMap := TNodeArrays.Create;
+  FMap := TNodeMap.Create;
 end;
 
 destructor TClumsyCrucible.Destroy;
@@ -114,116 +333,15 @@ begin
 end;
 
 procedure TClumsyCrucible.ProcessDataLine(const ALine: string);
-var
-  i: Integer;
-  nodes: TNodeArray;
 begin
-  FWidth := Length(ALine);
+  FMap.AddNodes(ALine);
-  SetLength(nodes, FWidth);
-  for i := 0 to FWidth - 1 do
-  begin
-    nodes[i].LocalHeatLoss := StrToInt(ALine[i + 1]);
-    nodes[i].Horizontal.IsTraversed := False;
-    nodes[i].Horizontal.NeedsUpdate := False;
-    nodes[i].Vertical.IsTraversed := False;
-    nodes[i].Vertical.NeedsUpdate := False;
-  end;
-  FMap.Add(nodes);
 end;
 
 procedure TClumsyCrucible.Finish;
-var
-  queue: TWorkQueue;
-  position: TPoint;
-  node: TNode;
-  newMinimum, acc: Cardinal;
-  i: Integer;
 begin
-  queue := TWorkQueue.Create;
+  FPart1 := FMap.FindMinimumPathLength(CMinStraight, CMaxStraight);
-
+  FMap.Reset;
-  // Initializes work queue with end node.
+  FPart2 := FMap.FindMinimumPathLength(CUltraMinStraight, CUltraMaxStraight);
-  FMap.Last[FWidth - 1].Horizontal.Minimum := 0;
-  FMap.Last[FWidth - 1].Horizontal.IsTraversed := True;
-  FMap.Last[FWidth - 1].Vertical := FMap.Last[FWidth - 1].Horizontal;
-  position := Point(FWidth - 1, FMap.Count - 1);
-  InvalidateHorizontalNeighbors(position, queue);
-  InvalidateVerticalNeighbors(position, queue);
-
-  // Processes work queue.
-  while queue.Count > 0 do
-  begin
-    position := queue.Dequeue;
-    node := FMap[position.Y][position.X];
-
-    // Updates horizontal data.
-    if node.Horizontal.NeedsUpdate then
-    begin
-      node.Horizontal.NeedsUpdate := False;
-
-      // Checks for better minimum in left direction.
-      newMinimum := Cardinal.MaxValue;
-      acc := 0;
-      for i := position.X - 1 downto Max(0, position.X - CMaxStraight) do
-      begin
-        Inc(acc, FMap[position.Y][i].LocalHeatLoss);
-        if FMap[position.Y][i].Vertical.IsTraversed then
-          newMinimum := Min(newMinimum, FMap[position.Y][i].Vertical.Minimum + acc);
-      end;
-      // Checks for better minimum in right direction.
-      acc := 0;
-      for i := position.X + 1 to Min(FWidth - 1, position.X + CMaxStraight) do
-      begin
-        Inc(acc, FMap[position.Y][i].LocalHeatLoss);
-        if FMap[position.Y][i].Vertical.IsTraversed then
-          newMinimum := Min(newMinimum, FMap[position.Y][i].Vertical.Minimum + acc);
-      end;
-      // Updates horizontal minimum and queues update for neighbors.
-      if not node.Horizontal.IsTraversed or (node.Horizontal.Minimum > newMinimum) then
-      begin
-        node.Horizontal.IsTraversed := True;
-        node.Horizontal.Minimum := newMinimum;
-        InvalidateVerticalNeighbors(position, queue);
-      end;
-    end;
-
-    // Updates vertical data.
-    if node.Vertical.NeedsUpdate then
-    begin
-      node.Vertical.NeedsUpdate := False;
-
-      // Checks for better minimum in up direction.
-      newMinimum := Cardinal.MaxValue;
-      acc := 0;
-      for i := position.Y - 1 downto Max(0, position.Y - CMaxStraight) do
-      begin
-        Inc(acc, FMap[i][position.X].LocalHeatLoss);
-        if FMap[i][position.X].Horizontal.IsTraversed then
-          newMinimum := Min(newMinimum, FMap[i][position.X].Horizontal.Minimum + acc);
-      end;
-      // Checks for better minimum in down direction.
-      acc := 0;
-      for i := position.Y + 1 to Min(FMap.Count - 1, position.Y + CMaxStraight) do
-      begin
-        Inc(acc, FMap[i][position.X].LocalHeatLoss);
-        if FMap[i][position.X].Horizontal.IsTraversed then
-          newMinimum := Min(newMinimum, FMap[i][position.X].Horizontal.Minimum + acc);
-      end;
-      // Updates vertical minimum and queues update for neighbors.
-      if not node.Vertical.IsTraversed or (node.Vertical.Minimum > newMinimum) then
-      begin
-        node.Vertical.IsTraversed := True;
-        node.Vertical.Minimum := newMinimum;
-        InvalidateHorizontalNeighbors(position, queue);
-      end;
-    end;
-
-    FMap[position.Y][position.X] := node;
-  end;
-
-  queue.Free;
-
-  node := FMap[0][0];
-  FPart1 := Min(node.Horizontal.Minimum, node.Vertical.Minimum);
 end;
 
 function TClumsyCrucible.GetDataFileName: string;

tests/UClumsyCrucibleTestCases.pas

@@ -33,6 +33,22 @@ type
     function CreateSolver: ISolver; override;
   published
     procedure TestPart1;
+    procedure TestPart2;
+  end;
+
+  { TExample2ClumsyCrucible }
+
+  TExample2ClumsyCrucible = class(TClumsyCrucible)
+    function GetDataFileName: string; override;
+  end;
+
+  { TClumsyCrucibleExample2TestCase }
+
+  TClumsyCrucibleExample2TestCase = class(TExampleEngineBaseTest)
+  protected
+    function CreateSolver: ISolver; override;
+  published
+    procedure TestPart2;
   end;
 
 implementation
@@ -49,8 +65,33 @@ begin
   AssertEquals(102, FSolver.GetResultPart1);
 end;
 
+procedure TClumsyCrucibleExampleTestCase.TestPart2;
+begin
+  AssertEquals(94, FSolver.GetResultPart2);
+end;
+
+{ TExample2ClumsyCrucible }
+
+function TExample2ClumsyCrucible.GetDataFileName: string;
+begin
+  Result := 'clumsy_crucible2.txt';
+end;
+
+{ TClumsyCrucibleExample2TestCase }
+
+function TClumsyCrucibleExample2TestCase.CreateSolver: ISolver;
+begin
+  Result := TExample2ClumsyCrucible.Create;
+end;
+
+procedure TClumsyCrucibleExample2TestCase.TestPart2;
+begin
+  AssertEquals(71, FSolver.GetResultPart2);
+end;
+
 initialization
 
   RegisterTest('TClumsyCrucible', TClumsyCrucibleExampleTestCase);
+  RegisterTest('TClumsyCrucible', TClumsyCrucibleExample2TestCase);
 end.