使用递归反转字符

Question

I can achieve reversing each word in a string and keep the order as well, but I believe it can be done quicker using recursion. At the moment I'm going through each character and flipping it, its not the best as it can be slow when the string is long. I'm working on an encryption algorithm if you want to know...

Example: 473hTml je31%@31#

This would result to: lmTh374 #13@%13ej

Any guidance or a good read would be great.

Answer 1

Don't use recursion: it won't be faster. Reversing a string is not a problem that requires recursion.

Actually, VB.Net has a StrReverse function, so I would advise you to just use that (combine with String.Split to break your string into words, and String.Join to put them back together).

Also, don't roll your own crypto - at least, not for protecting anything serious.

Answer 2

I'm no vb expert, but something like this should be a good start.

public string reverseWord(string data) {
    if (data.length == 1) {
        return data;
    } else {
        return data.Concat(data.Substring(-1), reverseWord(data.Substring(1));
    }
}

Answer 3

Behold, the recursive BogoFlip!

Module Module1
    Private rnd As New Random
    Dim str As String = "testing"

    Sub Main()
        Console.WriteLine(str & "     " & BogoFlip(str))
        Console.ReadLine()
    End Sub

    Public Function BogoFlip(originalString As String) As String
        Dim copy As String = originalString
        Dim flipped As String = ""
        Do Until copy.Length = 0
            Dim index As Integer = rnd.Next(copy.Length)
            flipped &= copy(index)
            copy = copy.Remove(index, 1)
        Loop
        If flipped = StrReverse(originalString) Then
            Return flipped
        Else
            Return BogoFlip(originalString)
        End If
    End Function
End Module

Please don't do this in real life... please please please please.