diff --git a/solvers/ULensLibrary.pas b/solvers/ULensLibrary.pas
index d6831d7..134dd7b 100644
--- a/solvers/ULensLibrary.pas
+++ b/solvers/ULensLibrary.pas
@@ -22,16 +22,45 @@ unit ULensLibrary;
 interface
 
 uses
-  Classes, SysUtils, USolver;
+  Classes, SysUtils, Generics.Collections, USolver;
 
 type
 
+  { TLens }
+
+  TLens = record
+    Key: string;
+    FocalLength: Byte;
+  end;
+
+  TBoxContent = specialize TList<TLens>;
+
+  TBoxes = specialize TObjectList<TBoxContent>;
+
+  { THashMap }
+
+  THashMap = class
+  private
+    FBoxes: TBoxes;
+    function IndexOf(const AHash: Byte; const AKey: string): Integer;
+  public
+    constructor Create;
+    destructor Destroy; override;
+    function CalcHash(const AInput: string): Byte;
+    procedure AddLens(const AKey: string; const AFocalLength: Byte);
+    procedure RemoveLens(const AKey: string);
+    function CalcFocusingPower: Int64;
+  end;
+
   { TLensLibrary }
 
   TLensLibrary = class(TSolver)
   private
-    function CalcHash(const AInput: string): Byte;
+    FHashMap: THashMap;
+    procedure ProcessInstruction(const AInstruction: string);
   public
+    constructor Create;
+    destructor Destroy; override;
     procedure ProcessDataLine(const ALine: string); override;
     procedure Finish; override;
     function GetDataFileName: string; override;
@@ -40,9 +69,41 @@ type
 
 implementation
 
-{ TLensLibrary }
+{ THashMap }
 
-function TLensLibrary.CalcHash(const AInput: string): Byte;
+function THashMap.IndexOf(const AHash: Byte; const AKey: string): Integer;
+var
+  i: Integer;
+begin
+  Result := -1;
+  i := 0;
+  while (i < FBoxes[AHash].Count) and (Result < 0) do
+  begin
+    if FBoxes[AHash][i].Key = AKey then
+      Result := i;
+    Inc(i);
+  end;
+end;
+
+constructor THashMap.Create;
+var
+  i: Integer;
+begin
+  FBoxes := TBoxes.Create;
+  FBoxes.Count := 256;
+  for i := 0 to FBoxes.Count - 1 do
+  begin
+    FBoxes[i] := TBoxContent.Create;
+  end;
+end;
+
+destructor THashMap.Destroy;
+begin
+  FBoxes.Free;
+  inherited Destroy;
+end;
+
+function THashMap.CalcHash(const AInput: string): Byte;
 var
   c: Char;
 begin
@@ -51,6 +112,72 @@ begin
     Result := ((Result + Ord(c)) * 17) and 255;
 end;
 
+procedure THashMap.AddLens(const AKey: string; const AFocalLength: Byte);
+var
+  hash: Byte;
+  i: Integer;
+  lens: TLens;
+begin
+  hash := CalcHash(AKey);
+  i := IndexOf(hash, AKey);
+  if i >= 0 then
+  begin
+    lens := FBoxes[hash][i];
+    lens.FocalLength := AFocalLength;
+    FBoxes[hash][i] := lens;
+  end
+  else begin
+    lens.Key := AKey;
+    lens.FocalLength := AFocalLength;
+    FBoxes[hash].Add(lens);
+  end;
+end;
+
+procedure THashMap.RemoveLens(const AKey: string);
+var
+  hash: Byte;
+  i: Integer;
+begin
+  hash := CalcHash(AKey);
+  i := IndexOf(hash, AKey);
+  if i >= 0 then
+    FBoxes[hash].Delete(i);
+end;
+
+function THashMap.CalcFocusingPower: Int64;
+var
+  i, j: Integer;
+begin
+  Result := 0;
+  for i := 0 to FBoxes.Count - 1 do
+    for j := 0 to FBoxes[i].Count - 1 do
+      Inc(Result, (i + 1) * (j + 1) * FBoxes[i][j].FocalLength);
+end;
+
+{ TLensLibrary }
+
+procedure TLensLibrary.ProcessInstruction(const AInstruction: string);
+var
+  len: Integer;
+begin
+  len := Length(AInstruction);
+  if AInstruction[len] = '-' then
+    FHashMap.RemoveLens(Copy(AInstruction, 1, len - 1))
+  else
+    FHashMap.AddLens(Copy(AInstruction, 1, len - 2), StrToInt(AInstruction[len]));
+end;
+
+constructor TLensLibrary.Create;
+begin
+  FHashMap := THashMap.Create;
+end;
+
+destructor TLensLibrary.Destroy;
+begin
+  FHashMap.Free;
+  inherited Destroy;
+end;
+
 procedure TLensLibrary.ProcessDataLine(const ALine: string);
 var
   split: TStringArray;
@@ -58,12 +185,15 @@ var
 begin
   split := ALine.Split(',');
   for s in split do
-    Inc(FPart1, CalcHash(s));
+  begin
+    Inc(FPart1, FHashMap.CalcHash(s));
+    ProcessInstruction(s);
+  end;
 end;
 
 procedure TLensLibrary.Finish;
 begin
-
+  FPart2 := FHashMap.CalcFocusingPower;
 end;
 
 function TLensLibrary.GetDataFileName: string;
diff --git a/tests/ULensLibraryTestCases.pas b/tests/ULensLibraryTestCases.pas
index f22a345..98abdfa 100644
--- a/tests/ULensLibraryTestCases.pas
+++ b/tests/ULensLibraryTestCases.pas
@@ -33,6 +33,7 @@ type
     function CreateSolver: ISolver; override;
   published
     procedure TestPart1;
+    procedure TestPart2;
   end;
 
   { TLensLibraryExampleTestCase }
@@ -42,6 +43,7 @@ type
     function CreateSolver: ISolver; override;
   published
     procedure TestPart1;
+    procedure TestPart2;
   end;
 
 implementation
@@ -58,6 +60,11 @@ begin
   AssertEquals(519041, FSolver.GetResultPart1);
 end;
 
+procedure TLensLibraryFullDataTestCase.TestPart2;
+begin
+  AssertEquals(260530, FSolver.GetResultPart2);
+end;
+
 { TLensLibraryExampleTestCase }
 
 function TLensLibraryExampleTestCase.CreateSolver: ISolver;
@@ -70,6 +77,11 @@ begin
   AssertEquals(1320, FSolver.GetResultPart1);
 end;
 
+procedure TLensLibraryExampleTestCase.TestPart2;
+begin
+  AssertEquals(145, FSolver.GetResultPart2);
+end;
+
 initialization
 
   RegisterTest(TLensLibraryFullDataTestCase);