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
) then
begin
Inc(m);
Inc(n);
if (Dchars[m] <> Dchars
) then
arrNext[m] := n
else
arrNext[m] := arrNext
;
end
else
begin
n := arrNext
;
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.