speed up function to reverse string

Question

I am using this function to reverse text but I am having a little issue with speed. for testing I have 130,000 characters text and its taking about 10 seconds. is it possible to speed it up? This questions is different than C# as its a vb.net

Function ReverseString(ByRef strString As String) As String
        Dim NextChr, TempString As String, StringLength, Count As Integer, NewString As String = Nothing

        TempString = strString
        StringLength = Len(TempString)
        Do While Count <= StringLength
            Count = Count + 1
            NextChr = Mid(TempString, Count, 1)
            NewString = NextChr & NewString
        Loop
        ReverseString = NewString
End Function

what about this questions [reverse a string using threads](http://stackoverflow.com/questions/10573286/reversing-a-string-using-threads) ? can that help? — Cacho Santa, Oct 17 '13 at 01:51
better suited for [codereview stackexchange](http://codereview.stackexchange.com/) ? — ethorn10, Oct 17 '13 at 01:53
This is getting closevoted and refered to a C# answer. Why was this tagged C#? — Jeroen Vannevel, Oct 17 '13 at 01:59

score 3 · Accepted Answer · answered Oct 17 '13 at 01:52

3

Try this:

 Function Reverse(ByVal value As String) As String
    ' Convert to char array.
    Dim arr() As Char = value.ToCharArray()
    ' Use Array.Reverse function.
    Array.Reverse(arr)
    ' Construct new string.
    Return New String(arr)
    End Function

Source: dot net perls

answered Oct 17 '13 at 01:52

Cacho Santa

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thanks! Updated with a vb example! – Cacho Santa Oct 17 '13 at 01:55
erm, why wouldn't you use @Makita's answer? – Mitch Wheat Oct 17 '13 at 02:15

score 3 · Answer 2 · answered Oct 17 '13 at 01:53

3

Maybe something along the lines of http://msdn.microsoft.com/en-us/library/e462ax87(v=vs.90).aspx? in VB:

Dim TestString As String = "ABCDEFG" 
' Returns "GFEDCBA". 
Dim revString As String = StrReverse(TestString)

answered Oct 17 '13 at 01:53

Makita

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score 2 · Answer 3 · answered Oct 17 '13 at 01:53

2

Function ReverseString(ByRef strString As String) As String
    Dim charArray As Char() = strString.ToCharArray()
    Array.Reverse(charArray )
    Dim strReversed As New String(charArray )
    ReverseString = strReversed
End Function

answered Oct 17 '13 at 01:53

Mitch Wheat

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score 0 · Answer 4 · answered Oct 17 '13 at 01:57

0

I would convert your string to a Character Array, then just call Array.Reverse.

I just tried this and it ran in: 0.862 seconds with a string that had 26,673,152 characters. Granted I'm on a pretyy fast PC but stil.

answered Oct 17 '13 at 01:57

Jack Marchetti

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score -1 · Answer 5 · answered Oct 17 '13 at 02:06

As it was said in other answers - it is better to use special function for this: StrReverse

but, if you want to have your own function, you can use this one, it should be faster:

Function ReverseString(ByRef strString As String) As String
    Dim builder As New System.Text.StringBuilder(strString.Length)
    Dim index As Integer = strString.Length - 1
    While index >= 0
        builder.Append(strString.Chars(index))
        index = index - 1
    End While
    ReverseString = builder.ToString
End Function

speed up function to reverse string

5 Answers5