《Delphi 算法与数据结构》学习与感悟[10]: 双向链表

如果在结构中再拿出 4 个字节的地址空间指向上一个节点, 就成了双向链表了.

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本例效果图:

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unit Unit1;



interface



uses

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

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    procedure FormCreate(Sender: TObject);

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



type

  PMyRec = ^MyRec;

  MyRec = record

    Name: string[8];

    Age : Word;

    Prev,Next: PMyRec; {上一个与下一个的结构指针}

  end;



var

  CurrentNode: PMyRec;



{建立双向链表}

procedure TForm1.FormCreate(Sender: TObject);

var

  PrevNode: PMyRec;

  i: Integer;

begin

  PrevNode := nil;

  for i := 65 to 71 do  {建七个节点, 准备用 AA, BB, CC, DD, EE, FF, GG 来指定 MyRec.Name }

  begin

    New(CurrentNode);

    CurrentNode.Name := Chr(i) + Chr(i);

    CurrentNode.Age := i;

    CurrentNode.Prev := PrevNode;

    if Assigned(PrevNode) then PrevNode.Next := CurrentNode;

    PrevNode := CurrentNode;

  end;



  Button1.Caption := '上一个';

  Button2.Caption := '下一个';

end;



{上一个}

procedure TForm1.Button1Click(Sender: TObject);

begin

  if Assigned(CurrentNode.Prev) then

  begin

    CurrentNode := CurrentNode.Prev;

    Text := CurrentNode.Name + #44 + IntToStr(CurrentNode.Age);

  end else Text := '这是第一个节点';

end;



{下一个}

procedure TForm1.Button2Click(Sender: TObject);

begin

  if Assigned(CurrentNode.Next) then

  begin

    CurrentNode := CurrentNode.Next;

    Text := CurrentNode.Name + #44 + IntToStr(CurrentNode.Age);

  end else Text := '这是最后一个节点';

end;



end.