Deque Encadeado

unit UDeque;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, StdCtrls, Buttons;

type
  No = Record
    V: String[10];
    L: Pointer;
  end;
  TFDeque = class(TForm)
    EditValor: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    EditDeque: TEdit;
    RG: TRadioGroup;
    BtInserir: TBitBtn;
    BtRetirar: TBitBtn;
    Panel1: TPanel;
    BitBtn3: TBitBtn;
    procedure FormShow(Sender: TObject);
    procedure BtInserirClick(Sender: TObject);
    procedure BtRetirarClick(Sender: TObject);
    procedure RGClick(Sender: TObject);
  private
    { Private declarations }
   procedure InsereDir;
   procedure InsereEsq;
   procedure MostraDeque;
   procedure RetiraEsq;
   procedure RetiraDir;
  public
    { Public declarations }
  end;

var
  FDeque: TFDeque;
  D, Aux: ^No;
  PDir,PEsq: Pointer;

implementation

{$R *.dfm}

procedure TFDeque.FormShow(Sender: TObject);
begin
   PDir := nil;
   PEsq := nil;
end;

procedure TFDeque.BtInserirClick(Sender: TObject);
begin
   if EditValor.Text = '' then
   begin
      ShowMessage('Valor inválido!'+#10+
                  'Digite um valor.');
      EditValor.SetFocus;
   end
   else
   begin
      try
        New(D);
      Except
        ShowMessage('Erro ao criar nó');
        EditValor.Clear;
        EditValor.SetFocus;
        Exit;
      end;
      if RG.ItemIndex = 0 then
         InsereEsq
      else
         InsereDir;
   end;
end;

procedure TFDeque.InsereDir;
begin
   D.V := EditValor.Text;
   if PDir = Nil then
   begin
      PEsq := D;
      D.L := PEsq;
   end
   else
   begin
      Aux := PDir;
      Aux.L := D;
      D.L := PEsq;
   end;
   PDir := D;
   MostraDeque;
   EditValor.Clear;
   EditValor.SetFocus;
end;

procedure TFDeque.InsereEsq;
begin
  if PEsq = nil then
  begin
     PDir := D;
     D.L := D;
  end
  else
  begin
     Aux := D;
     Aux.L := PEsq;
  end;
  D.V := EditValor.Text;
  PEsq := D;
  Aux := PDir;
  Aux.L := PEsq;
  MostraDeque;
  EditValor.Clear;
  EditValor.SetFocus;
end;

procedure TFDeque.MostraDeque;
begin
  Aux := PEsq;
  EditDeque.Text := '| ';
  While Aux <> PDir do
  begin
     EditDeque.Text := EditDeque.Text + Aux.V + ' | ';
     Aux := Aux.L;
  end;
  EditDeque.Text := EditDeque.Text + Aux.V + ' | ';
end;

procedure TFDeque.RetiraEsq;
begin
   if PEsq = nil then
      ShowMessage('Deque vazio!')
   else
   begin
      if PEsq = PDir then
      begin
         PEsq := nil;
         PDir := nil;
         EditDeque.Clear;
      end
      else
      begin
         Aux := PEsq;
         PEsq := Aux.L;
         Aux := nil;
         Aux := PDir;
         Aux.L := PEsq;
         MostraDeque;
      end;
   end;
   EditValor.SetFocus;
end;

procedure TFDeque.RetiraDir;
begin
   if PDir = nil then
   begin
      ShowMessage('Deque vazio!');
      EditValor.SetFocus;
   end
   else
   begin
      if PDir = PEsq then
      begin
         PDir := nil;
         PEsq := nil;
         EditDeque.Clear;
         EditValor.SetFocus;
      end
      else
      begin
         Aux := PEsq;
         While Aux.L <> PDir do
            Aux := Aux.L;
         PDir := nil;
         PDir := Aux;
         Aux.L := PEsq;
         BtRetirar.SetFocus;
         MostraDeque;
      end;
   end;
end;

procedure TFDeque.BtRetirarClick(Sender: TObject);
begin
   if RG.ItemIndex = 0 then
      RetiraEsq
   else
      RetiraDir;
end;

procedure TFDeque.RGClick(Sender: TObject);
begin
   EditValor.SetFocus;
end;

end.