KMP(字符串匹配)算法

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

  private

    { Private declarations }

    //模式数组

    arrNext : array of Integer;

    //主串数组

    Schars : array of AnsiChar;

    //字串数组

    Dchars : array of AnsiChar;



    //获取模式数组

    procedure GetNext;

    //查找匹配

    function KPM(sPos:Integer):integer;

  public

    { Public declarations }

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



{ TForm1 }



procedure TForm1.GetNext;

var

  len,m,n:Integer;

begin

  m := 0;

  n := -1;

  len := Length(Dchars);

  SetLength(arrNext,len);

  arrNext[0] := -1;

  while (m+1)<= len do

  begin

    if (n = -1) or (Dchars[m] = Dchars[n]) then

    begin

      Inc(m);

      Inc(n);

      if (Dchars[m] <> Dchars[n]) then

        arrNext[m] := n

      else

        arrNext[m] := arrNext[n];

    end

    else

    begin

      n := arrNext[n];

    end;

  end;

end;



function TForm1.KPM(sPos:Integer): integer;

var

  i,j:Integer;

begin

  Result := 0;

  i := sPos;

  j := 0;

  while (i < Length(Schars)) and (j < Length(Dchars)) do

  begin

    if (Schars[i] = Dchars[j]) then

    begin

      Inc(i);

      Inc(j);

    end

    else

    begin

      Result := Result + j - arrNext[j];

      if arrNext[j] <> -1 then

      begin

        j := arrNext[j];

      end

      else

      begin

        j := 0;

        Inc(i);

      end;

    end;

  end;

  if j <> Length(Dchars) then

    Result := -1;

end;



procedure TForm1.Button1Click(Sender: TObject);

var

  s,d:string;

  index : Integer;

begin

  s := '中华人民共和国';

  d := '人民';

  index := -1;

  SetLength(Schars,Length(s));

  SetLength(Dchars,Length(d));

  Move(s[1],Schars[0],Length(s));

  Move(d[1],Dchars[0],Length(d));

  GetNext;

  index := KPM(0);

  if index = -1 then

    ShowMessage('没有找到匹配!')

  else

    ShowMessage('从第'+IntToStr(index+1)+'个字符开始匹配');

end;



end.

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