Question

如何用DELPHI编写不用第三变量，将两个变量的值交换啊

那位高人能解决一下哦，谢谢．．．．

Answer 1

可以使用异或来一个巧妙的解决,代码如下(仅仅贴单元文件)
(Delphi 7 + Windows XP sp2)

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 }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure Swap(var a:integer;var b: integer);
begin
  a := a xor b;
  b := a xor b;
  a := a xor b;
end;
 
procedure TForm1.Button1Click(Sender: TObject);
var
  n1,n2:integer;
begin
  n1 := 100;
  n2 := 200;
  ShowMessage('n1='+IntToStr(n1) + ' ' + 'n2=' + IntToStr(n2));
  Swap(n1,n2);
  ShowMessage('n1='+IntToStr(n1) + ' ' + 'n2=' + IntToStr(n2));
end;
 
end.

Answer 2

举个例子:
var a, b : string; list,list1 : tstrings;
begin
a := 'eee';
b := 'aaa';
list := tstringlist.Create;
list1 := tstringlist.Create;
list.Add(a);
list1.Add(b);
a := list1.Text;
b := list.Text;
end;

Answer 3

a := a+b;
b := a-b;
a := a-b;