Search Arraylist in Arraylist.

[Simon Says]

Hi all,

I've an arraylist A1 that contains {0,1,2,3,4,5,9, 8,7}
I've another arraylist A2 that contains {4,5,9}

I would like to search whether if A2 is present in A1 and maybe return the
first occurance index. Can anyone advise on this?

Thanks,
Simon

[Cor Ligthert [MVP]]

Simon,

I would use this method.

http://msdn2.microsoft.com/en-us/lib...t.indexof.aspx

I hope this helps,

Cor

[Simon Says]

Cor,

I've tried this but doesn't seem to be working. I think what this function
does is that it searches through each items in my A1 for the exact matches
of the whole of A2. That is to say:

Items in A1: Items in A2:
0 {4,5,9}
1
2
3
4
5
9
8
7

It searches each items in A1 for an arraylist of {4,5,9}. Instead, I need
something like

Items in A1: Items in A2:
0 4
1 5
2 9
3
4
5
9
8
7

Sorry I can't explain too well, but any other ways?

--Simon

"Cor Ligthert [MVP]" <no************ @planet.nl> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Simon,

I would use this method.

http://msdn2.microsoft.com/en-us/lib...t.indexof.aspx

I hope this helps,

Cor

[Andrew Morton]

Simon Says wrote:

Hi all,

I've an arraylist A1 that contains {0,1,2,3,4,5,9, 8,7}
I've another arraylist A2 that contains {4,5,9}

I would like to search whether if A2 is present in A1 and maybe
return the first occurance index. Can anyone advise on this?

Are you saying that the elements in A1 and A2 are unique and in order? Are
A1 and A2 of trivial length?

if count(A2)>count (A1) then no match
take first element of A2 and find it in A1
check there are enough elements remaining in A1 for a match to be possible
take subsequent elements of A2 and compare them to subsequent elements of A1

Andrew

[Cor Ligthert [MVP]]

Simon,

First of all, I do probably not understand what you want.

A try
\\\
Dim a1 As New ArrayList
a1.AddRange(New Object() {0, 1, 2, 3, 4, 5, 9, 6, 8, 7})
Dim a2 As New ArrayList
a2.AddRange(New Object() {4, 5, 9})
For i As Integer = 0 To a2.Count - 1
Dim ind As Integer = a1.IndexOf(a2(i ))
If ind > -1 Then
MessageBox.Show (ind.ToString)
End If
Next
///

I hope this helps,

cor

[Simon Says]

Can't understand myself too :-) Anyway, I've tried something like,

//
dim a1 as new ArrayList
dim a2 as new ArrayList

a1.AddRange(New Integer() {0,1,2,3,4,5,9, 8,7})
a2.AddRange(New Integer() {4,5,9})

if a1.IndexOf(a2) > -1 then
call msgbox("Found")
else
call msgbox("Not Found")
End if
//

The result I got is "Not Found". I think with IndexOf function it searches
throught a1 in following sequence:

0 ----> {4,5,9}
1 ----> {4,5,9}
2 ----> {4,5,9}
....
7 ----> {4,5,9}

Therefore, I will not be able to get a match. If Cor's method is the only
way, I will try to change my implementation as O(n*m) performance isn't
quite impressive - O(n) for IndexOf function call and O(m) for looping
through a2.

Any more insights?

--Simon

"Andrew Morton" <ak*@in-press.co.uk.inv alid> wrote in message
news:Ow******** *****@TK2MSFTNG P12.phx.gbl...

Simon Says wrote:

Hi all,

I've an arraylist A1 that contains {0,1,2,3,4,5,9, 8,7}
I've another arraylist A2 that contains {4,5,9}

I would like to search whether if A2 is present in A1 and maybe
return the first occurance index. Can anyone advise on this?

Are you saying that the elements in A1 and A2 are unique and in order? Are
A1 and A2 of trivial length?

if count(A2)>count (A1) then no match
take first element of A2 and find it in A1
check there are enough elements remaining in A1 for a match to be possible
take subsequent elements of A2 and compare them to subsequent elements of
A1

Andrew

[Andrew Morton]

> "Andrew Morton" wrote

Are A1 and A2 of trivial length?

If so, convert them to strings (somehow) and use string functions on them.

Using ArrayList.Index Of(someArrayLis t) won't work because it looks for an
ArrayList entity within your ArrayList, but the entities in your array list
are numbers.

Andrew

[Simon Says]

Hi Andrew,

I can't convert them to string as the data I'm working on is network
streaming bytes that contains compressed data. Converting them to string
will sort of mess up my compressed data. All my streaming bytes will be
stored in A1 which will varies in size, and I will check for delimiter -
A2 - which will be of fixed length.

I've already worked out a helper function as suggested by Cor, but the
O(n*m) performance just worries me a little.

--Simon

"Andrew Morton" <ak*@in-press.co.uk.inv alid> wrote in message
news:e%******** ********@TK2MSF TNGP14.phx.gbl. ..

"Andrew Morton" wrote

Are A1 and A2 of trivial length?

If so, convert them to strings (somehow) and use string functions on them.

Using ArrayList.Index Of(someArrayLis t) won't work because it looks for an
ArrayList entity within your ArrayList, but the entities in your array
list are numbers.

Andrew

[Andrew Morton]

Simon Says wrote:

I can't convert them to string as the data I'm working on is network
streaming bytes that contains compressed data. Converting them to
string will sort of mess up my compressed data. All my streaming
bytes will be stored in A1 which will varies in size, and I will
check for delimiter - A2 - which will be of fixed length.

Imagine streem is your incoming data and eos is the sequence indicating the
end of the packet in the stream. In your case they would be bytes, but for
my convenience I've used strings, so remember that VB strings have their
first character at position 1, not 0.

Dim streem As String = "46324682492147 47473773"
Dim eos As String = "324"
Dim c As String

Dim eosPos As Integer = 1 ' position in eos
Dim streemPos As Integer = 1 ' position in streem
Dim dataEnd As Integer ' the length of the data, less the eos marker

While streemPos <= Len(streem)
streemPos += 1
c = Mid(streem, streemPos, 1)
If c = Mid(eos, eosPos, 1) Then
eosPos += 1
If eosPos > Len(eos) Then
' we have found the end of the data
dataEnd = streemPos - Len(eos)
Exit While
End If
Else
eosPos = 1
End If
End While

Andrew

[Simon Says]

Since my data is in byte, my values are in the range of 0-255. By converting
my stream of data to string (also tried based64String) will totally messed
up my data.

What I've tried was convert my byte() to string (using
Convert.ToBased 64String) then find the delimiter position and extract out
the data portion, then convert the data portion back to byte(). It just
messed up my compressed data.
"Andrew Morton" <ak*@in-press.co.uk.inv alid> wrote in message
news:uL******** ******@TK2MSFTN GP11.phx.gbl...

Simon Says wrote:

I can't convert them to string as the data I'm working on is network
streaming bytes that contains compressed data. Converting them to
string will sort of mess up my compressed data. All my streaming
bytes will be stored in A1 which will varies in size, and I will
check for delimiter - A2 - which will be of fixed length.

Imagine streem is your incoming data and eos is the sequence indicating
the end of the packet in the stream. In your case they would be bytes, but
for my convenience I've used strings, so remember that VB strings have
their first character at position 1, not 0.

Dim streem As String = "46324682492147 47473773"
Dim eos As String = "324"
Dim c As String

Dim eosPos As Integer = 1 ' position in eos
Dim streemPos As Integer = 1 ' position in streem
Dim dataEnd As Integer ' the length of the data, less the eos marker

While streemPos <= Len(streem)
streemPos += 1
c = Mid(streem, streemPos, 1)
If c = Mid(eos, eosPos, 1) Then
eosPos += 1
If eosPos > Len(eos) Then
' we have found the end of the data
dataEnd = streemPos - Len(eos)
Exit While
End If
Else
eosPos = 1
End If
End While

Andrew