Boyer Moore Algorithmus

[Ginko]

Hier ist mal mein Versuchsaufbau:

Delphi-Quellcode:

unit Unit1;
{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls, BMH, strutils;

type

  { TForm1 }

  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Edit1: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

function NextPosBMH(SearchStr, Str: string; Position: Integer): Integer;
begin
  Delete(Str, 1, Position - 1);
  Result := Search_BMH_Unrolled(Str,SearchStr);
  if Result = 0 then Exit;
  if (Length(Str) > 0) and (Length(SearchStr) > 0) then
    Result := Result + Position + 1;
end;

Function CountWordsStd(Const text, wort : String) : Integer;
Var
  i : Integer;
Begin
  i:=1;
  Result := 0;
  repeat
    i := PosEx(wort,text,i)+1;
    if i > 1 then inc(Result) else exit;
  until false
End;

Function CountWordsStdBMH(Const text, wort : String) : Integer;
Var
  i : Integer;
Begin
  i:=1;
  Result := 0;
  repeat
    i := NextPosBMH(wort,text,i)+1;
    if i > 1 then inc(Result) else exit;
  until false
End;

procedure TForm1.Button1Click(Sender: TObject); //Std Pos
var
  Filestream : TFileStream;
  SuchWort, SuchText: String;
begin
  SuchWort:= Edit1.Text;

  Filestream:=TFileStream.Create('test.txt',fmOpenRead);
  Try
    SetLength(SuchText,Filestream.Size);
    Filestream.Read(SuchText[1],Length(SuchText));
    Label1.Caption:= IntToStr(CountWordsStd(SuchText,SuchWort));
  Finally
    Filestream.Free;
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);   // BMH
var
  Filestream : TFileStream;
  SuchWort, SuchText: String;
begin
  SuchWort:= Edit1.Text;

  Filestream:=TFileStream.Create('test.txt',fmOpenRead);
  Try
    SetLength(SuchText,Filestream.Size);
    Filestream.Read(SuchText[1],Length(SuchText));
    Label1.Caption:= IntToStr(CountWordsStdBMH(SuchText,SuchWort));
  Finally
    Filestream.Free;
  end;
end;
end.

Textdatei test.txt:

Code:

Point

Line

Square

Point Point

Triangle

Line

Point

Die Funktion, die mit der Standard Pos arbeitet findet für "Point" -> 4
Die Funktion, die mit BMH arbeitet findet für "Point" -> 1