String instance count

[Jon]

I want to count the number of instances of a certain string(delimite r) in
another string. I didn't see a function to do this in the framework (if
there is, please point me to it). If not, could someone let me know if the
method I've used below is efficient or if there is a better way to do it, as
these will be rather large strings I'm searching in. Thanks

Public Shared Function CountDelimiter( ByVal strInput As String, ByVal
strDelimiter As String) As Int32
Dim iStart As Int32, iCount As Int32, iResult As Int32

'Set our vars to base values
iStart = 1
iCount = 0

Do
'iResult becomes the position where delimiter is found. If 0, not
found.
iResult = InStr(iStart, strInput, strDelimiter)
If iResult = 0 Then Exit Do
'Increment our count var for each time it is found
iCount += 1
'Increment our next start position to be the next char after the
currently found position
iStart = iResult + 1
Loop

Return iCount
End Function



--
--------
Jon Rosenberg

[Cor]

Re: String instance count

Hi Jon,
I am too always looking for that, but when I did look at your code I thought
this stupid
\\\\\\\
Dim a As String = "abaaa abbba babaabaabaab"
Dim b As String() = Split(a, "ab")
MessageBox.Show ((b.Length - 1).ToString)
///////
When you don't get a better answer you can try it, doing some little tests
it did work.
It is stupid of course.
Cor

[Herfried K. Wagner [MVP]]

Re: String instance count

"Cor" <non@non.com> scripsit:[color=blue]
> I am too always looking for that, but when I did look at your code I thought
> this stupid
> \\\\\\\
> Dim a As String = "abaaa abbba babaabaabaab"
> Dim b As String() = Split(a, "ab")
> MessageBox.Show ((b.Length - 1).ToString)
> ///////
> When you don't get a better answer you can try it, doing some little tests
> it did work.
> It is stupid of course.[/color]

Yes, it works. But I think it's not the best solution if you split a 10
MB string.

;-)

--
Herfried K. Wagner
MVP · VB Classic, VB.NET
<http://www.mvps.org/dotnet>

[Cor]

Re: String instance count

Herfried,
The other samples does as far as I can see a loop from 1 increment per
character each time.
I am not so sure if that is faster,
But ok lets make a deal, do you type a 10Mb string, than will I make the
testprogram.
Cor

[Jay B. Harlow [MVP - Outlook]]

Re: String instance count

Cor,
When I need a 10Mb string, I normally use a loop with a StringBuilder. As I
suspect posting a 10M string to the newsgroup might be blocked ;-)

Something like:

Dim sb As New System.Text.Str ingBuilder(10 * 1024 * 1024)

For i As Integer = 0 To 1024 * 1024
sb.Append("0123 456789")
Next

Dim s As String = sb.ToString()

Sometimes I will use a System.Random object to indirectly create random text
to append instead of the fixed values.

A week or two ago the topic of counting occurrences of delimiters in strings
came up in the C# newsgroup, someone suggested using a
System.Text.Reg ularExpression. RegEx object. One of the individuals did some
testing, the RegEx method was about 100 times slower than the for loop. They
did not try the Split method. This was based on occurrences of individual
characters, not occurrences of strings. See "string manipulation" from 25
Sept 2003 in the microsoft.publi c.dotnet.langua ges.csharp newsgroup if you
are interested.

Out of curiosity it would be interesting to see what the difference between
splitting, counting & reg expressions performance wise... On both VB.NET
2002 & VB.NET 2003...

Hope this helps
Jay

"Cor" <non@non.com> wrote in message
news:3f7c99b5$0 $18955$48b97d01 @reader22.wxs.n l...[color=blue]
> Herfried,
> The other samples does as far as I can see a loop from 1 increment per
> character each time.
> I am not so sure if that is faster,
> But ok lets make a deal, do you type a 10Mb string, than will I make the
> testprogram.
> Cor
>
>[/color]

[Herfried K. Wagner [MVP]]

Re: String instance count

"Cor" <non@non.com> scripsit:[color=blue]
> The other samples does as far as I can see a loop from 1 increment per
> character each time.
> I am not so sure if that is faster,
> But ok lets make a deal, do you type a 10Mb string, than will I make the
> testprogram.[/color]

Splitting a 10 MB sting will increase memory usage for the application
to 20 MB. That's what I wanted to say.

:-)

--
Herfried K. Wagner
MVP · VB Classic, VB.NET
<http://www.mvps.org/dotnet>

[Cor]

Re: String instance count

Hi Jay,
Me too,
I shall try to make a test and give the results here.
But I don't have vb2002 and I am always to lazy to make a regex.
But I have a link, someone did send for a regex maker, maybe I can use that.
Otherwise it is only the two methods, (maybe three so that I can use
Microsoft Visual basic too)
I thought that Jeremy Cowles said in the chat that they where so terrible
slow.

I make that string myself of course, but look at the post I send to
Herfried.

Normaly you see the results tomorrow.
Cor

[Cor]

Re: String instance count

Hi Herfried,
I forgot to tell, when you are ready with typing that teststring from 10Mb.
please don't zip it in the post, just paste it in.
With those problems from the newserver from Microsoft, I think a zip file
never arives.
Cor

[Herfried K. Wagner [MVP]]

Re: String instance count

"Cor" <non@non.com> scripsit:[color=blue]
> I forgot to tell, when you are ready with typing that teststring from 10Mb.
> please don't zip it in the post, just paste it in.
> With those problems from the newserver from Microsoft, I think a zip file
> never arives.[/color]

I think there will be a size limitation...

--
Herfried K. Wagner
MVP · VB Classic, VB.NET
<http://www.mvps.org/dotnet>

[Cor]

Re: String instance count

Herfried,
I have seen you are very quick in typing. That will give no size problem.
Cor

[Chris Dunaway]

Re: String instance count

"Jon" <ruffles_@msn.c om> wrote in
news:vnovsedmlp cd57@corp.super news.com:
[color=blue]
> I want to count the number of instances of a certain string(delimite r)[/color]

One method would be to use a regular expression and then check the
Matches.Count property:


'\\\\
Dim sSource As String = "abbabaabbababa babbababbabbaab ababbbabbababab babab"
Dim rx As New System.Text.Reg ularExpressions .Regex("a")

MsgBox("Number of matches = " & CStr(rx.Matches (sSource).Count ))
'////

[therealpmuk]

I also have an interest in this, needing to check for (and count) the number of occurrences of various errors in an error.log file.

The files can get quite large, but I have achieved the following results with a filesize of just over 11 Meg:-


Count 79608

TimeBySplit 22187500 Long
TimeByLoop 28750000 Long
TimeByRegEx 1093750 Long


Count 113

TimeBySplit 2031250 Long
TimeByLoop 28125000 Long
TimeByRegEx 156250 Long

Timing done using System.DateTime .Now.Ticks.

As you can see, the Regular Expression method consistently yields the fastest results.