# 《Delphi 算法与数据结构》学习与感悟[8]: 单向链表的添加、删除与遍历

unit Unit1;

interface

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

type
TForm1 = class(TForm)
Memo1: TMemo;
Button1: TButton;
Button2: TButton;
Button3: TButton;
Button4: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{\$R *.dfm}

type
PMyRec = ^MyRec;
MyRec = record
Name: string[8];
Age : Word;
end;

var
CurrentNode, FirstNode: PMyRec;

{建立链表}
procedure TForm1.FormCreate(Sender: TObject);
begin
New(FirstNode);
FirstNode.Name := '李四';
FirstNode.Age  := 44;
CurrentNode := FirstNode;

New(FirstNode);
FirstNode.Name := '张三';
FirstNode.Age  := 33;
CurrentNode := FirstNode;

New(FirstNode);
FirstNode.Name := '钱二';
FirstNode.Age  := 22;
CurrentNode := FirstNode;

New(FirstNode);
FirstNode.Name := '赵一';
FirstNode.Age  := 11;
CurrentNode := FirstNode;

Button1.Caption := '遍历链表';
Button2.Caption := '插入节点';
Button3.Caption := '删除节点';
Button4.Caption := '删除链表';

Memo1.Align := alLeft;
Memo1.ScrollBars := ssVertical;
end;

{遍历链表节点}
procedure TForm1.Button1Click(Sender: TObject);
begin
Memo1.Clear;
CurrentNode := FirstNode;
while Assigned(CurrentNode) do
begin
end;
end;

{插入节点}
procedure TForm1.Button2Click(Sender: TObject);
var
NewNode: PMyRec;
begin
{譬如是插入在第二个节点后面}
New(NewNode);
NewNode.Name := 'AAA';
NewNode.Age  := 100;

{前后连起来}

{调用遍历}
Button1.Click;
end;

{删除节点}
procedure TForm1.Button3Click(Sender: TObject);
begin
{譬如是删除第二个节点}
CurrentNode := FirstNode.Link;        {让 CurrentNode 指向第二个节点}
if Assigned(CurrentNode.Link) then    {如果 CurrentNode 还有下一个}
begin
Dispose(CurrentNode);               {释放用 New 申请的内存}
end;

Button1.Click;
end;

{销毁链表, 释放所有节点}
procedure TForm1.Button4Click(Sender: TObject);
begin
CurrentNode := FirstNode;     {从链头向下删除}
while Assigned(FirstNode) do
begin
CurrentNode := FirstNode;