|
web
newsgroups
|
|||||||||||||||||||||||
|
|||||||||||||||||||||||
Count Instances Of String Within StringIs there an efficient line of code to count the number of instances of one
string within another. If I have the sentence: "I want to go to the park, and then go home." It would give me a count of 2 for the word "go" Derek use the string compare method
Dim s As String = "I want to go to the park, and then go home." MsgBox((String.Compare(s, "go") + 1).ToString & " Occurances of go") regards Michel Posseth [MCP] Show quoteHide quote "Derek Hart" <derekmh***@yahoo.com> schreef in bericht news:%23x99NifcGHA.3952@TK2MSFTNGP04.phx.gbl... > Is there an efficient line of code to count the number of instances of one > string within another. > > If I have the sentence: > "I want to go to the park, and then go home." > > It would give me a count of 2 for the word "go" > > Derek > Ahum :-(
Embarased mode : Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim s As String = "I want to go to the park, and then go home." MsgBox(countsubstrings(s, "go")) End Sub Function countsubstrings(ByVal source As String, ByVal search As String) As Integer Dim count As Integer = -1 Dim index As Integer = -1 Do count += 1 index = source.IndexOf(search, index + 1) Loop Until index < 0 Return count End Function this wil work Show quoteHide quote "Michel Posseth [MCP]" <mic***@posseth.com> schreef in bericht news:OmwGe9fcGHA.4108@TK2MSFTNGP03.phx.gbl... > use the string compare method > > Dim s As String = "I want to go to the park, and then go home." > MsgBox((String.Compare(s, "go") + 1).ToString & " Occurances of > go") > > regards > > Michel Posseth [MCP] > > > "Derek Hart" <derekmh***@yahoo.com> schreef in bericht > news:%23x99NifcGHA.3952@TK2MSFTNGP04.phx.gbl... >> Is there an efficient line of code to count the number of instances of >> one string within another. >> >> If I have the sentence: >> "I want to go to the park, and then go home." >> >> It would give me a count of 2 for the word "go" >> >> Derek >> > > I don't believe there is a way to put it in one line (at least not in
VB.NET, other languages might have a built-in method that does this or possibly give you the ability to put multiple commands on one line), but here is a simple loop that does what you want in VB.NET: Dim teststring As String = "I want to go to the park, and then go home." Dim i As Integer = -1 Dim stringcount As Integer = 0 While teststring.IndexOf("go", i + 1) <> -1 stringcount += 1 i = teststring.IndexOf("go", i + 1) End While You can also write it as a function, which I would strongly suggest if you plan on doing this more than once: Public Function CountInstances(ByVal lookfor As String, ByVal lookin As String) As Integer Dim stringcount As Integer = 0 Dim i As Integer = -1 While lookin.IndexOf(lookfor, i + 1) <> -1 stringcount += 1 i = lookin.IndexOf(lookfor, i + 1) End While Return stringcount End Function Writing it as a function will require the few lines of code to write the function, but after that you can call it from just one line, making your code simpler to write and debug: stringcount = CountInstances("go", teststring) If you have any questions, feel free to ask. Good Luck! Show quoteHide quote "Derek Hart" <derekmh***@yahoo.com> wrote in message news:%23x99NifcGHA.3952@TK2MSFTNGP04.phx.gbl... > Is there an efficient line of code to count the number of instances of one > string within another. > > If I have the sentence: > "I want to go to the park, and then go home." > > It would give me a count of 2 for the word "go" > > Derek > Derek,
You could also use regular expressions to match the instances of a string inside another string. I *believe* the pattern I use returns all instances of 'go' surrounded by spaces, but then again I'm not very good with RegEx yet. Imports System.Text.RegularExpressions Module main Sub main() Dim strtoSearch As String = "I want to go to the park, and then go home." Console.WriteLine(GetStringOccurences(strtoSearch, "go").ToString) Console.ReadLine() End Sub Private Function GetStringOccurences(ByVal searchString, ByVal searchWord) As Integer Dim r As New Regex(String.Format("\s{0}\s", searchWord)) Return r.Matches(searchString).Count End Function End Module Dim str$ = "I want to go to the park, and then go home."
Dim findstr$ = "go" Dim wordcount% = (Len(str) - Len(Replace(str, findstr, ""))) / Len(findstr) MsgBox(wordcount) Show quoteHide quote "Derek Hart" <derekmh***@yahoo.com> wrote in message news:%23x99NifcGHA.3952@TK2MSFTNGP04.phx.gbl... > Is there an efficient line of code to count the number of instances of one > string within another. > > If I have the sentence: > "I want to go to the park, and then go home." > > It would give me a count of 2 for the word "go" > > Derek > Derek,
As once tested in this newsgroup is this the fastest method for that (I have changed the fieldnames now so watch that). \\\ Public Function CountString(ByVal SearchItem As String, ByVal ToCountString _ As String) As Integer Dim Start as Integer = 1 Dim Count as Interger = 0 Dim Result as Interger Do Result = InStr(Start, SearchItem, ToCountString) If Result = 0 Then Exit Do Count += 1 Start = Result + 1 Loop Return Count End Function /// If the ToCountString becomes a ToCountChar than there are better methods. I hope this helps, Cor Show quoteHide quote "Derek Hart" <derekmh***@yahoo.com> schreef in bericht news:%23x99NifcGHA.3952@TK2MSFTNGP04.phx.gbl... > Is there an efficient line of code to count the number of instances of one > string within another. > > If I have the sentence: > "I want to go to the park, and then go home." > > It would give me a count of 2 for the word "go" > > Derek > Cor ...
surely the following will be much faster. string tofind = "test" string foo = "testtest footestfoo"; string changed = foo.Replace(tofind, ""); return (foo.length - changed.length) / tofind.length Cheers, Greg Young MVP - C# Show quoteHide quote "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> wrote in message news:u9riclmcGHA.3908@TK2MSFTNGP04.phx.gbl... > Derek, > > As once tested in this newsgroup is this the fastest method for that (I > have changed the fieldnames now so watch that). > \\\ > Public Function CountString(ByVal SearchItem As String, ByVal > ToCountString _ > As String) As Integer > Dim Start as Integer = 1 > Dim Count as Interger = 0 > Dim Result as Interger > Do > Result = InStr(Start, SearchItem, ToCountString) > If Result = 0 Then Exit Do > Count += 1 > Start = Result + 1 > Loop > Return Count > End Function > /// > > If the ToCountString becomes a ToCountChar than there are better methods. > > I hope this helps, > > Cor > > "Derek Hart" <derekmh***@yahoo.com> schreef in bericht > news:%23x99NifcGHA.3952@TK2MSFTNGP04.phx.gbl... >> Is there an efficient line of code to count the number of instances of >> one string within another. >> >> If I have the sentence: >> "I want to go to the park, and then go home." >> >> It would give me a count of 2 for the word "go" >> >> Derek >> > > Greg,
I am sure it will not. > Although some little changes can make that it probably does.> surely the following will be much faster. > string tofind = "test" > string foo = "testtest footestfoo"; > string changed = foo.Replace(tofind, ""); > return (foo.length - changed.length) / tofind.length > :-) I said I thought yesterday already that I found it a nice idea.I forgot that with some changes you can use it for this as well. Cor It does probably, I misreaded something, I am testing it, what it real means
because I am in doubt about some side effects. Cor Show quoteHide quote "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... > Greg, > > I am sure it will not. > >> >> surely the following will be much faster. >> string tofind = "test" >> string foo = "testtest footestfoo"; >> string changed = foo.Replace(tofind, ""); >> return (foo.length - changed.length) / tofind.length >> > Although some little changes can make that it probably does. > > :-) > > I said I thought yesterday already that I found it a nice idea. > > I forgot that with some changes you can use it for this as well. > > Cor > The problem exists in both methods in use ..
If I want to look for the word "GO" and I also have worgs like gong or pogo, they will be detected as being instances of the word, an easy way to work around this is to pass in spaces i.e. " go " but then I will not detect patterns such as "lets go!" because there is no traling space or "go to the beach" because there is no leading space. It is these items that make the implementation of an algorithm like this tricky. Cheers, Greg Young MVP - C# Show quoteHide quote "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> wrote in message news:%23mJl6BocGHA.1208@TK2MSFTNGP02.phx.gbl... > It does probably, I misreaded something, I am testing it, what it real > means because I am in doubt about some side effects. > > Cor > > "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht > news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >> Greg, >> >> I am sure it will not. >> >>> >>> surely the following will be much faster. >>> string tofind = "test" >>> string foo = "testtest footestfoo"; >>> string changed = foo.Replace(tofind, ""); >>> return (foo.length - changed.length) / tofind.length >>> >> Although some little changes can make that it probably does. >> >> :-) >> >> I said I thought yesterday already that I found it a nice idea. >> >> I forgot that with some changes you can use it for this as well. >> >> Cor >> > > That is neatly handled by a regular expression. The /b code matches a
word boundary. RegEx re = new RegEx("/b" + RegEx.Escape(tofind) + "/b"); int found = re.Matches(foo).Count; Greg Young wrote: Show quoteHide quote > The problem exists in both methods in use .. > > If I want to look for the word "GO" and I also have worgs like gong or pogo, > they will be detected as being instances of the word, an easy way to work > around this is to pass in spaces i.e. " go " but then I will not detect > patterns such as "lets go!" because there is no traling space or "go to the > beach" because there is no leading space. > > It is these items that make the implementation of an algorithm like this > tricky. > > Cheers, > > Greg Young > MVP - C# > "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> wrote in message > news:%23mJl6BocGHA.1208@TK2MSFTNGP02.phx.gbl... >> It does probably, I misreaded something, I am testing it, what it real >> means because I am in doubt about some side effects. >> >> Cor >> >> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>> Greg, >>> >>> I am sure it will not. >>> >>>> surely the following will be much faster. >>>> string tofind = "test" >>>> string foo = "testtest footestfoo"; >>>> string changed = foo.Replace(tofind, ""); >>>> return (foo.length - changed.length) / tofind.length >>>> >>> Although some little changes can make that it probably does. >>> >>> :-) >>> >>> I said I thought yesterday already that I found it a nice idea. >>> >>> I forgot that with some changes you can use it for this as well. >>> >>> Cor >>> >> > > Thanks for this, Goran. I had posted something similar earlier, but I
had used the "/s" which did not correctly catch instances of the string at the start or end of a sentence. Is the RegEx.Escape( ) there to account for any characters in your toFind variable that are RegEx operators? jayeldee wrote:
> Is the RegEx.Escape( ) there to account for any characters in your Exactly. Although a typical word wouldn't contain any, it keeps the > toFind variable that are RegEx operators? regular expression from crashing if it would. The replace method might be more efficient for short strings, but the
method using InStr (or IndexOf) scales better, as it doesn't create another string that is almost as big as the string being searched. Cor Ligthert [MVP] wrote: Show quoteHide quote > It does probably, I misreaded something, I am testing it, what it real means > because I am in doubt about some side effects. > > Cor > > "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht > news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >> Greg, >> >> I am sure it will not. >> >>> surely the following will be much faster. >>> string tofind = "test" >>> string foo = "testtest footestfoo"; >>> string changed = foo.Replace(tofind, ""); >>> return (foo.length - changed.length) / tofind.length >>> >> Although some little changes can make that it probably does. >> >> :-) >> >> I said I thought yesterday already that I found it a nice idea. >> >> I forgot that with some changes you can use it for this as well. >> >> Cor >> > > Goran,
Indexof with strings is twice as slow as InStr. With char it beats InStr that it is not to mention, but it is than of course comparing apples with pears, because InStr(char) does not exist. Cor Show quoteHide quote "Göran Andersson" <gu***@guffa.com> schreef in bericht news:eHs4RZocGHA.3952@TK2MSFTNGP04.phx.gbl... > The replace method might be more efficient for short strings, but the > method using InStr (or IndexOf) scales better, as it doesn't create > another string that is almost as big as the string being searched. > > Cor Ligthert [MVP] wrote: >> It does probably, I misreaded something, I am testing it, what it real >> means because I am in doubt about some side effects. >> >> Cor >> >> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>> Greg, >>> >>> I am sure it will not. >>> >>>> surely the following will be much faster. >>>> string tofind = "test" >>>> string foo = "testtest footestfoo"; >>>> string changed = foo.Replace(tofind, ""); >>>> return (foo.length - changed.length) / tofind.length >>>> >>> Although some little changes can make that it probably does. >>> >>> :-) >>> >>> I said I thought yesterday already that I found it a nice idea. >>> >>> I forgot that with some changes you can use it for this as well. >>> >>> Cor >>> >> If you have come to that conclusion I think that you haven't used them
in the same way, as both internally calls CurrentCulture.CompareInfo.IndexOf. InStr only has more overhead. Cor Ligthert [MVP] wrote: Show quoteHide quote > Goran, > > Indexof with strings is twice as slow as InStr. > > With char it beats InStr that it is not to mention, but it is than of course > comparing apples with pears, because InStr(char) does not exist. > > Cor > > "Göran Andersson" <gu***@guffa.com> schreef in bericht > news:eHs4RZocGHA.3952@TK2MSFTNGP04.phx.gbl... >> The replace method might be more efficient for short strings, but the >> method using InStr (or IndexOf) scales better, as it doesn't create >> another string that is almost as big as the string being searched. >> >> Cor Ligthert [MVP] wrote: >>> It does probably, I misreaded something, I am testing it, what it real >>> means because I am in doubt about some side effects. >>> >>> Cor >>> >>> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >>> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>>> Greg, >>>> >>>> I am sure it will not. >>>> >>>>> surely the following will be much faster. >>>>> string tofind = "test" >>>>> string foo = "testtest footestfoo"; >>>>> string changed = foo.Replace(tofind, ""); >>>>> return (foo.length - changed.length) / tofind.length >>>>> >>>> Although some little changes can make that it probably does. >>>> >>>> :-) >>>> >>>> I said I thought yesterday already that I found it a nice idea. >>>> >>>> I forgot that with some changes you can use it for this as well. >>>> >>>> Cor >>>> > Goran,
Did you test it, I had before I tested it the same idea as you. Instr is a very simple instruction, while indexof has more complex posibilities. Those should be tested of course. And as I said not with char. Cor Show quoteHide quote "Göran Andersson" <gu***@guffa.com> schreef in bericht news:O4nWCPpcGHA.2068@TK2MSFTNGP02.phx.gbl... > If you have come to that conclusion I think that you haven't used them in > the same way, as both internally calls CurrentCulture.CompareInfo.IndexOf. > InStr only has more overhead. > > Cor Ligthert [MVP] wrote: >> Goran, >> >> Indexof with strings is twice as slow as InStr. >> >> With char it beats InStr that it is not to mention, but it is than of >> course comparing apples with pears, because InStr(char) does not exist. >> >> Cor >> >> "Göran Andersson" <gu***@guffa.com> schreef in bericht >> news:eHs4RZocGHA.3952@TK2MSFTNGP04.phx.gbl... >>> The replace method might be more efficient for short strings, but the >>> method using InStr (or IndexOf) scales better, as it doesn't create >>> another string that is almost as big as the string being searched. >>> >>> Cor Ligthert [MVP] wrote: >>>> It does probably, I misreaded something, I am testing it, what it real >>>> means because I am in doubt about some side effects. >>>> >>>> Cor >>>> >>>> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >>>> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>>>> Greg, >>>>> >>>>> I am sure it will not. >>>>> >>>>>> surely the following will be much faster. >>>>>> string tofind = "test" >>>>>> string foo = "testtest footestfoo"; >>>>>> string changed = foo.Replace(tofind, ""); >>>>>> return (foo.length - changed.length) / tofind.length >>>>>> >>>>> Although some little changes can make that it probably does. >>>>> >>>>> :-) >>>>> >>>>> I said I thought yesterday already that I found it a nice idea. >>>>> >>>>> I forgot that with some changes you can use it for this as well. >>>>> >>>>> Cor >>>>> >> It would be interresting to se how you did the test. When I test it I
get the result that IndexOf is slightly faster, but they never differ more than a few percent. Here is what I tested: HighResolutionClock clock; int pos; double time1, time2; string text, find; text = "askdjf iuqwh peha sduuhböaos9 döqown eiluhas9ödhföoasid öfoiajsd fä0sd föoiqwe fuh asilduhfasudh föoiqiweöf oihas dlifyg asliudhf öoasihdf h"; find = "duhf"; clock = new HighResolutionClock(); clock.Reset(); for (int i = 0; i < 1000000; i++) pos = Strings.InStr(2, text, find, CompareMethod.Text); time1 = clock.Seconds; clock.Reset(); for (int i = 0; i < 1000000; i++) pos = text.IndexOf(find, 1, StringComparison.CurrentCultureIgnoreCase); time2 = clock.Seconds; Typical result: time1: 3.589 time2: 3.519 (I can post the HighResolutionClock class if you want. It uses the QueryPerformanceCounter method in kernel32.dll.) Cor Ligthert [MVP] wrote: Show quoteHide quote > Goran, > > Did you test it, I had before I tested it the same idea as you. Instr is a > very simple instruction, while indexof has more complex posibilities. Those > should be tested of course. > > And as I said not with char. > > Cor > > "Göran Andersson" <gu***@guffa.com> schreef in bericht > news:O4nWCPpcGHA.2068@TK2MSFTNGP02.phx.gbl... >> If you have come to that conclusion I think that you haven't used them in >> the same way, as both internally calls CurrentCulture.CompareInfo.IndexOf. >> InStr only has more overhead. >> >> Cor Ligthert [MVP] wrote: >>> Goran, >>> >>> Indexof with strings is twice as slow as InStr. >>> >>> With char it beats InStr that it is not to mention, but it is than of >>> course comparing apples with pears, because InStr(char) does not exist. >>> >>> Cor >>> >>> "Göran Andersson" <gu***@guffa.com> schreef in bericht >>> news:eHs4RZocGHA.3952@TK2MSFTNGP04.phx.gbl... >>>> The replace method might be more efficient for short strings, but the >>>> method using InStr (or IndexOf) scales better, as it doesn't create >>>> another string that is almost as big as the string being searched. >>>> >>>> Cor Ligthert [MVP] wrote: >>>>> It does probably, I misreaded something, I am testing it, what it real >>>>> means because I am in doubt about some side effects. >>>>> >>>>> Cor >>>>> >>>>> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >>>>> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>>>>> Greg, >>>>>> >>>>>> I am sure it will not. >>>>>> >>>>>>> surely the following will be much faster. >>>>>>> string tofind = "test" >>>>>>> string foo = "testtest footestfoo"; >>>>>>> string changed = foo.Replace(tofind, ""); >>>>>>> return (foo.length - changed.length) / tofind.length >>>>>>> >>>>>> Although some little changes can make that it probably does. >>>>>> >>>>>> :-) >>>>>> >>>>>> I said I thought yesterday already that I found it a nice idea. >>>>>> >>>>>> I forgot that with some changes you can use it for this as well. >>>>>> >>>>>> Cor >>>>>> > >
http://groups.google.com/group/microsoft.public.dotnet.languages.vb/msg/315c33cc87237dbf
By the way we are still waiting on that typed string from Herfried, Cor Show quoteHide quote "Göran Andersson" <gu***@guffa.com> schreef in bericht news:%23KnwevqcGHA.4312@TK2MSFTNGP05.phx.gbl... > It would be interresting to se how you did the test. When I test it I get > the result that IndexOf is slightly faster, but they never differ more > than a few percent. > > Here is what I tested: > > > HighResolutionClock clock; > int pos; > double time1, time2; > string text, find; > > text = "askdjf iuqwh peha sduuhböaos9 döqown eiluhas9ödhföoasid öfoiajsd > fä0sd föoiqwe fuh asilduhfasudh föoiqiweöf oihas dlifyg asliudhf öoasihdf > h"; > find = "duhf"; > > clock = new HighResolutionClock(); > > clock.Reset(); > for (int i = 0; i < 1000000; i++) pos = Strings.InStr(2, text, find, > CompareMethod.Text); > time1 = clock.Seconds; > > clock.Reset(); > for (int i = 0; i < 1000000; i++) pos = text.IndexOf(find, 1, > StringComparison.CurrentCultureIgnoreCase); > time2 = clock.Seconds; > > > Typical result: > > time1: 3.589 > time2: 3.519 > > > (I can post the HighResolutionClock class if you want. It uses the > QueryPerformanceCounter method in kernel32.dll.) > > > Cor Ligthert [MVP] wrote: >> Goran, >> >> Did you test it, I had before I tested it the same idea as you. Instr is >> a very simple instruction, while indexof has more complex posibilities. >> Those should be tested of course. >> >> And as I said not with char. >> >> Cor >> >> "Göran Andersson" <gu***@guffa.com> schreef in bericht >> news:O4nWCPpcGHA.2068@TK2MSFTNGP02.phx.gbl... >>> If you have come to that conclusion I think that you haven't used them >>> in the same way, as both internally calls >>> CurrentCulture.CompareInfo.IndexOf. InStr only has more overhead. >>> >>> Cor Ligthert [MVP] wrote: >>>> Goran, >>>> >>>> Indexof with strings is twice as slow as InStr. >>>> >>>> With char it beats InStr that it is not to mention, but it is than of >>>> course comparing apples with pears, because InStr(char) does not exist. >>>> >>>> Cor >>>> >>>> "Göran Andersson" <gu***@guffa.com> schreef in bericht >>>> news:eHs4RZocGHA.3952@TK2MSFTNGP04.phx.gbl... >>>>> The replace method might be more efficient for short strings, but the >>>>> method using InStr (or IndexOf) scales better, as it doesn't create >>>>> another string that is almost as big as the string being searched. >>>>> >>>>> Cor Ligthert [MVP] wrote: >>>>>> It does probably, I misreaded something, I am testing it, what it >>>>>> real means because I am in doubt about some side effects. >>>>>> >>>>>> Cor >>>>>> >>>>>> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >>>>>> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>>>>>> Greg, >>>>>>> >>>>>>> I am sure it will not. >>>>>>> >>>>>>>> surely the following will be much faster. >>>>>>>> string tofind = "test" >>>>>>>> string foo = "testtest footestfoo"; >>>>>>>> string changed = foo.Replace(tofind, ""); >>>>>>>> return (foo.length - changed.length) / tofind.length >>>>>>>> >>>>>>> Although some little changes can make that it probably does. >>>>>>> >>>>>>> :-) >>>>>>> >>>>>>> I said I thought yesterday already that I found it a nice idea. >>>>>>> >>>>>>> I forgot that with some changes you can use it for this as well. >>>>>>> >>>>>>> Cor >>>>>>> >> On 2006-05-08, Göran Andersson <gu***@guffa.com> wrote:
> If you have come to that conclusion I think that you haven't used them A slight correction, by default InStr uses InvariantCulture, while> in the same way, as both internally calls > CurrentCulture.CompareInfo.IndexOf. InStr only has more overhead. String.IndexOf always uses CurrentCulture. Show quoteHide quote > > Cor Ligthert [MVP] wrote: >> Goran, >> >> Indexof with strings is twice as slow as InStr. >> >> With char it beats InStr that it is not to mention, but it is than of course >> comparing apples with pears, because InStr(char) does not exist. >> >> Cor >> >> "Göran Andersson" <gu***@guffa.com> schreef in bericht >> news:eHs4RZocGHA.3952@TK2MSFTNGP04.phx.gbl... >>> The replace method might be more efficient for short strings, but the >>> method using InStr (or IndexOf) scales better, as it doesn't create >>> another string that is almost as big as the string being searched. >>> >>> Cor Ligthert [MVP] wrote: >>>> It does probably, I misreaded something, I am testing it, what it real >>>> means because I am in doubt about some side effects. >>>> >>>> Cor >>>> >>>> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >>>> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>>>> Greg, >>>>> >>>>> I am sure it will not. >>>>> >>>>>> surely the following will be much faster. >>>>>> string tofind = "test" >>>>>> string foo = "testtest footestfoo"; >>>>>> string changed = foo.Replace(tofind, ""); >>>>>> return (foo.length - changed.length) / tofind.length >>>>>> >>>>> Although some little changes can make that it probably does. >>>>> >>>>> :-) >>>>> >>>>> I said I thought yesterday already that I found it a nice idea. >>>>> >>>>> I forgot that with some changes you can use it for this as well. >>>>> >>>>> Cor >>>>> >> david wrote:
> On 2006-05-08, Göran Andersson <gu***@guffa.com> wrote: Yes, if you do a binary search it will use InvariantCulture. So will >> If you have come to that conclusion I think that you haven't used them >> in the same way, as both internally calls >> CurrentCulture.CompareInfo.IndexOf. InStr only has more overhead. > > A slight correction, by default InStr uses InvariantCulture, while > String.IndexOf always uses CurrentCulture. > IndexOf. You are correct Goran.
Cheers, Greg Show quoteHide quote "Göran Andersson" <gu***@guffa.com> wrote in message news:eHs4RZocGHA.3952@TK2MSFTNGP04.phx.gbl... > The replace method might be more efficient for short strings, but the > method using InStr (or IndexOf) scales better, as it doesn't create > another string that is almost as big as the string being searched. > > Cor Ligthert [MVP] wrote: >> It does probably, I misreaded something, I am testing it, what it real >> means because I am in doubt about some side effects. >> >> Cor >> >> "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> schreef in bericht >> news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >>> Greg, >>> >>> I am sure it will not. >>> >>>> surely the following will be much faster. >>>> string tofind = "test" >>>> string foo = "testtest footestfoo"; >>>> string changed = foo.Replace(tofind, ""); >>>> return (foo.length - changed.length) / tofind.length >>>> >>> Although some little changes can make that it probably does. >>> >>> :-) >>> >>> I said I thought yesterday already that I found it a nice idea. >>> >>> I forgot that with some changes you can use it for this as well. >>> >>> Cor >>> >> I am a strong believer in the pragmatic programmer idea of ... if in doubt
test it ... added a loop to run 100 tests, countstring2 beat countstring 100/100 times ... even with varying data counts (including no data)... perhaps you have some code shoing the opposite? Cheers, Greg Young MVP - C# Module Module1 Public Function CountString(ByVal SearchItem As String, ByVal ToCountString As String) As Integer Dim Start As Integer = 1 Dim Count As Integer = 0 Dim Result As Integer Do Result = InStr(Start, SearchItem, ToCountString) If Result = 0 Then Exit Do Count += 1 Start = Result + 1 Loop Return Count End Function Public Function CountString2(ByVal SearchItem As String, ByVal ToCountString As String) As Integer Dim tmp As String = SearchItem.Replace(ToCountString, "") Return (SearchItem.Length - tmp.Length) / ToCountString.Length End Function Sub Main() Dim ToCountString As String = "test" Dim SearchItem As String = "testtesttestfootesttesttest" Dim i As Integer Dim starttime As DateTime = DateTime.Now Dim endtime As DateTime For i = 0 To 1000000 CountString(SearchItem, ToCountString) Next endtime = DateTime.Now Console.WriteLine("CountString - " & (endtime - starttime).ToString()) starttime = DateTime.Now For i = 0 To 1000000 CountString2(SearchItem, ToCountString) Next endtime = DateTime.Now Console.WriteLine("CountString2 - " & (endtime - starttime).ToString()) End Sub End Module Show quoteHide quote "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> wrote in message news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... > Greg, > > I am sure it will not. > >> >> surely the following will be much faster. >> string tofind = "test" >> string foo = "testtest footestfoo"; >> string changed = foo.Replace(tofind, ""); >> return (foo.length - changed.length) / tofind.length >> > Although some little changes can make that it probably does. > > :-) > > I said I thought yesterday already that I found it a nice idea. > > I forgot that with some changes you can use it for this as well. > > Cor > Greg,
The problem as you wrote was my idea too, however that side effect was not there in my simple test. 100* a string "Cor Greg GregCor CorGreg ", that I tested 100.000 times each time both methods and counting the time. The method with the replace beats the methode with the moving instr at least about 5:7. Both methods are therefore quicker than any I have seen until now, while that replace method is for me now the fastest. Cor Show quoteHide quote "Greg Young" <DruckDruckGo***@hotmail.com> schreef in bericht news:uVRYdEocGHA.3352@TK2MSFTNGP03.phx.gbl... >I am a strong believer in the pragmatic programmer idea of ... if in doubt >test it ... > > added a loop to run 100 tests, countstring2 beat countstring 100/100 times > .. even with varying data counts (including no data)... perhaps you have > some code shoing the opposite? > > Cheers, > > Greg Young > MVP - C# > > Module Module1 > > Public Function CountString(ByVal SearchItem As String, ByVal > ToCountString As String) As Integer > Dim Start As Integer = 1 > Dim Count As Integer = 0 > Dim Result As Integer > Do > Result = InStr(Start, SearchItem, ToCountString) > If Result = 0 Then Exit Do > Count += 1 > Start = Result + 1 > Loop > Return Count > End Function > > Public Function CountString2(ByVal SearchItem As String, ByVal > ToCountString As String) As Integer > Dim tmp As String = SearchItem.Replace(ToCountString, "") > Return (SearchItem.Length - tmp.Length) / ToCountString.Length > End Function > > Sub Main() > Dim ToCountString As String = "test" > Dim SearchItem As String = "testtesttestfootesttesttest" > Dim i As Integer > Dim starttime As DateTime = DateTime.Now > Dim endtime As DateTime > For i = 0 To 1000000 > CountString(SearchItem, ToCountString) > Next > endtime = DateTime.Now > Console.WriteLine("CountString - " & (endtime - > starttime).ToString()) > starttime = DateTime.Now > For i = 0 To 1000000 > CountString2(SearchItem, ToCountString) > Next > endtime = DateTime.Now > Console.WriteLine("CountString2 - " & (endtime - > starttime).ToString()) > > End Sub > > End Module > "Cor Ligthert [MVP]" <notmyfirstn***@planet.nl> wrote in message > news:OIiJw3ncGHA.1208@TK2MSFTNGP02.phx.gbl... >> Greg, >> >> I am sure it will not. >> >>> >>> surely the following will be much faster. >>> string tofind = "test" >>> string foo = "testtest footestfoo"; >>> string changed = foo.Replace(tofind, ""); >>> return (foo.length - changed.length) / tofind.length >>> >> Although some little changes can make that it probably does. >> >> :-) >> >> I said I thought yesterday already that I found it a nice idea. >> >> I forgot that with some changes you can use it for this as well. >> >> Cor >> > > 
Other interesting topics
Large text file import: MVP question
Clearing a custom array 'OpenFileDialog crashes for no reason? Removing array entry so cumbersome?? Declaring a garbage collector SMTP won't send until thread terminates regular expressions Which one is the Bluetooth DLL? Text into HTML Font to bold, italic, underline only |
|||||||||||||||||||||||
