Zhd

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    memoEncrypt: TMemo;
    memoDecrypt: TMemo;
    Edit1: TEdit;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

type
   ChArr = array of char;

function ArrToStr(TempArr: ChArr; Str: string): string;
var
   i, j: Integer;
   TempStr: string;
begin
   SetLength(TempArr, Length(Str));
   for i := 0 to Length(Str) - 1 do
         TempStr := TempStr + TempArr[i];
   ArrToStr := TempStr;
end;

function NumerateStr(Str: string; Key: Integer): string;
var
   i, j: Integer;
   NewArr: ChArr;
   NewStr: string;
begin
   SetLength(NewArr, Length(Str));
   i := 1;
   while (i <= Length(Str)) do
   begin
      for j := 1 to Key do
      begin
         NewArr[i - 1] := chr(j);
         inc(i);
      end;
      for j := Key - 1 downto 2 do
      begin
         NewArr[i - 1] := chr(j);
         inc(i);
      end;
   end;
   NumerateStr := ArrToStr(NewArr, Str);
end;

function Encrypt(Str: string; SourceStr: string; Key: integer): string;
var
   i, j, m: Integer;
   NewStr: string;
begin
   i := 1;
   j := 1;
   m := 1;
   NewStr := SourceStr;
   while (j <= Key) do
   begin
      while (i <= Length(Str)) do
      begin
         if (Str[i] = chr(j)) then
         begin
            NewStr[m] := SourceStr[i];
            inc(m);
         end;
         inc(i);
      end;
      i := 1;
      inc(j);
   end;
   Encrypt := NewStr;
end;

function Decrypt(NumStr: string; SourceStr: string; Key: integer): string;
var
   i, j, m: Integer;
begin
   i := 1;
   j := 1;
   m := 1;
   while (j <= Key) do
   begin
      while (i <= Length(SourceStr)) do
      begin
         if (NumStr[i] = chr(j)) then
         begin
            NumStr[i] := SourceStr[m];
            inc(m);
         end;
         inc(i);
      end;
      i := 1;
      inc(j);
   end;
   Decrypt := NumStr;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
   SourceStr, NumStr, NewStr: string;
begin
   SourceStr := memoEncrypt.Text;
   NumStr := NumerateStr(SourceStr, strtoint(edit1.Text));
   NewStr := Encrypt(NumStr, SourceStr, strtoint(edit1.Text));
   memoDecrypt.Text := NewStr;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
   SourceStr, NumStr: string;
begin
   SourceStr := memoDecrypt.Text;
   NumStr := NumerateStr(SourceStr, strtoint(edit1.Text));
   NumStr := Decrypt(NumStr, SourceStr, strtoint(edit1.Text));
   memoDecrypt.Text := NumStr;
end;

end.