学步园

 1 var
 2   Form1: TForm1;
 3   Len10NumberList:TStringList;
 4 
 5 implementation
 6 
 7 {$R *.dfm}
 8 
 9 procedure TForm1.FormCreate(Sender: TObject);
10 begin
11         Len10NumberList:=TStringList.Create;
12         Randomize;
13 end;
14 
15 function GenerateLen10Number:Int64;
16 var
17         rn1, rn2, rn3 : Int64;
18 begin
19         repeat
20                 rn1 := Random( 94868 );
21                 rn2 := Random( 94868 );
22                 rn3 := Random( 62575 );
23                 Result:=  1000000000 + //既然是10位数这个是基数部分
24                           rn1 * rn2 + rn3;  //这一行随机数的范围囊括了: 0 到 8999999999 (94868*94868+62575=8999999999)
25         until Len10NumberList.IndexOf( IntToStr(Result) )=-1;//用INDEXOF的效率极高，
26                                                              //用FOR循环是效率极低的，
27                                                              //尤其是STRINGLIST中的条目很多的时候！！！
28                                                              //这句为精华之处！！！
29         Len10NumberList.Add( IntToStr(Result) );//加到列表中以便下次查询，避免重复.
30 end;
31 
32 procedure TForm1.FormDestroy(Sender: TObject);
33 begin
34         Len10NumberList.Free;//也可以做保存后FREE之
35 end;
36 
37 procedure TForm1.Button1Click(Sender: TObject);
38 begin
39         ShowMessage( IntToStr( GenerateLen10Number ) );
40 end;  
41 

 

关于indexof:

 

Call IndexOf to obtain the position of the first occurrence of the string S, or of a string that differs from S only by case. IndexOf returns the 0-based index of the string. Thus, if S matches the first string in the list, IndexOf returns 0, if S is the second string, IndexOf returns 1, and so on. If the string is not in the string list, IndexOf returns -1.

Note:  If the string appears in the list more than once, IndexOf returns the position of the first occurrence.