binaryseach of an arraylist

[Bernie Yaeger]

I'm having difficulty searching an arraylist for certain values that are in
another arraylist. Essentially, I want to load the second arraylist with
only one of each of the possible elements in the first arraylist. Thus if
singlearraylist contains "ww", "l2", "s1", "ww", "cc", "s1" I only want
marraylist to have "ww", "l2", "s1", "cc". The search seems to fail
regardless what I do, and the result is that marraylist has virtually all of
the elements from singlearraylist. Here's my code:
For i = 0 To singlearraylist.Count - 1

searchobj = singlearraylist(i)

ifind = marraylist.BinarySearch(searchobj)

If ifind < 0 Then ' ie, not found

marraylist.Add(singlearraylist(i))

End If

Next

Tx for any help.

Bernie Yaeger

[Bernie Yaeger]

OK, figured it out - I have to continually sort the arraylist as I add
items - binarysearch only works against a sorted arraylist.

Tx - Bernie

"Bernie Yaeger" <be*****@cherwellinc.com> wrote in message
news:%2****************@TK2MSFTNGP11.phx.gbl...

I'm having difficulty searching an arraylist for certain values that are in another arraylist. Essentially, I want to load the second arraylist with
only one of each of the possible elements in the first arraylist. Thus if
singlearraylist contains "ww", "l2", "s1", "ww", "cc", "s1" I only want
marraylist to have "ww", "l2", "s1", "cc". The search seems to fail
regardless what I do, and the result is that marraylist has virtually all of the elements from singlearraylist. Here's my code:
For i = 0 To singlearraylist.Count - 1

searchobj = singlearraylist(i)

ifind = marraylist.BinarySearch(searchobj)

If ifind < 0 Then ' ie, not found

marraylist.Add(singlearraylist(i))

End If

Next

Tx for any help.

Bernie Yaeger

[Fergus Cooney]

Hi Bernie,

There's a more efficient way of doing this which doesn't requires any
searching or sorting (except once at the start).

Sort the singlearraylist. Then go through the sorted array copying values
unless they have already been copied.

Dim sLastValue As String = ""
For Each sValue As String In singlearraylist
If sValue <> sLastValue Then
marraylist.Add (sValue)
sLastValue = sValue
End If
Next

Regards,
Fergus

[Jay B. Harlow [MVP - Outlook]]

Bernie,
In addition to Fergus's comments.

Have you considered using a SortedList instead of an ArrayList.

As SortedLists are automatically sorted and support finding the item by a
key.

The problem is if the objects you are dealing with do not have a good 'key'
or do not make good 'keys'.

If the objects don't really have keys I would use Fergus's idea.

Hope this helps
Jay

"Bernie Yaeger" <be*****@cherwellinc.com> wrote in message
news:Oc**************@TK2MSFTNGP11.phx.gbl...

OK, figured it out - I have to continually sort the arraylist as I add
items - binarysearch only works against a sorted arraylist.

Tx - Bernie

"Bernie Yaeger" <be*****@cherwellinc.com> wrote in message
news:%2****************@TK2MSFTNGP11.phx.gbl...

I'm having difficulty searching an arraylist for certain values that are in

another arraylist. Essentially, I want to load the second arraylist with only one of each of the possible elements in the first arraylist. Thus if singlearraylist contains "ww", "l2", "s1", "ww", "cc", "s1" I only want
marraylist to have "ww", "l2", "s1", "cc". The search seems to fail
regardless what I do, and the result is that marraylist has virtually

all of

the elements from singlearraylist. Here's my code:
For i = 0 To singlearraylist.Count - 1

searchobj = singlearraylist(i)

ifind = marraylist.BinarySearch(searchobj)

If ifind < 0 Then ' ie, not found

marraylist.Add(singlearraylist(i))

End If

Next

Tx for any help.

Bernie Yaeger

[Bernie Yaeger]

Tx Fergus, Jay,

A sortedlist would not apply here, correct, as making good keys would be a
problem. Tx to you both.

Bernie

"Jay B. Harlow [MVP - Outlook]" <Ja********@email.msn.com> wrote in message
news:uy**************@TK2MSFTNGP11.phx.gbl...

Bernie,
In addition to Fergus's comments.

Have you considered using a SortedList instead of an ArrayList.

As SortedLists are automatically sorted and support finding the item by a
key.

The problem is if the objects you are dealing with do not have a good 'key' or do not make good 'keys'.

If the objects don't really have keys I would use Fergus's idea.

Hope this helps
Jay

"Bernie Yaeger" <be*****@cherwellinc.com> wrote in message
news:Oc**************@TK2MSFTNGP11.phx.gbl...

OK, figured it out - I have to continually sort the arraylist as I add
items - binarysearch only works against a sorted arraylist.

Tx - Bernie

"Bernie Yaeger" <be*****@cherwellinc.com> wrote in message
news:%2****************@TK2MSFTNGP11.phx.gbl...

I'm having difficulty searching an arraylist for certain values that are

in

another arraylist. Essentially, I want to load the second arraylist with only one of each of the possible elements in the first arraylist.

Thus

if singlearraylist contains "ww", "l2", "s1", "ww", "cc", "s1" I only

want marraylist to have "ww", "l2", "s1", "cc". The search seems to fail
regardless what I do, and the result is that marraylist has virtually

all

of

the elements from singlearraylist. Here's my code:
For i = 0 To singlearraylist.Count - 1

searchobj = singlearraylist(i)

ifind = marraylist.BinarySearch(searchobj)

If ifind < 0 Then ' ie, not found

marraylist.Add(singlearraylist(i))

End If

Next

Tx for any help.

Bernie Yaeger