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Двоичный поиск для TListView

01.01.2007
{+------------------------------------------------------------ 
| Function ListviewBinarySearch
|
| Parameters :
| listview: listview to search, assumed to be sorted, must
| be <> nil.
| Item : item caption to search for, cannot be empty
| index : returns the index of the found item, or the
| index where the item should be inserted if it is not
| already in the list.
| Returns : True if there is an item with the passed caption
| in the list, false otherwise.
| Description:
| Uses a binary search and assumes that the listview is sorted
| ascending on the caption of the listitems. The search is
| case-sensitive, like the default alpha-sort routine used by
| the TListview class.
| Note:
| We use the lstrcmp function for string comparison since it
| is the function used by the default alpha sort routine. If
| the listview is sorted by another means (e.g. OnCompare event)
| this needs to be changed, the comparison method used must
| always be the same one used to sort the listview, or the
| search will not work!
| Error Conditions: none
| Created: 31.10.99 by P. Below
+------------------------------------------------------------}
 
 
function ListviewBinarySearch(listview: TListview; const Item: string;
   
var Index: Integer): Boolean;
 
var
   
First, last, pivot, res: Integer;
 
begin
   
Assert(Assigned(listview));
   
Assert(Length(item) > 0);
 
   
Result := False;
   
Index  := 0;
   
if listview.Items.Count = 0 then Exit;
 
   
First := 0;
   
last  := listview.Items.Count - 1;
   repeat
     pivot
:= (First + last) div 2;
     res  
:= lstrcmp(PChar(item), PChar(listview.Items[pivot].Caption));
     
if res = 0 then
     
begin
       
{ Found the item, return its index and exit. }
       
Index  := pivot;
       
Result := True;
       
Break;
     
end { If }
     
else if res > 0 then
     
begin
       
{ Item is larger than item at pivot }
       
First := pivot + 1;
     
end { If }
     
else
     
begin
       
{ Item is smaller than item at pivot }
       
last := pivot - 1;
     
end;
   
until last < First;
   
Index := First;
 
end; { ListviewBinarySearch }

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