Mega Code Archive
Perform a binary seach on a TListview
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Title: perform a binary seach on a TListview?
{+------------------------------------------------------------
| 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
Index := First;
end; { ListviewBinarySearch }
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