random characters

Okay, so below we have a string:

`1234567890-=~!@#$%^&*()_+qwertyuiop[]\QWERTYUIOP{}|asdfghjkl;'ASDFGHJKL:"zxcvbnm,./ZXCVBNM<>?

For each character of this string I want a new character out of the string and then remove the character from the list of characters that still maybe used for other characters. It may not get the same character, you could basically just call this encryption, but it's not what I am making. I don't want to waste my time doing this one hour while VB can do this for me in <1 second.

So any code would be very appreciated!

A hint

Code:

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    Dim prng As New Random

    Private Sub Button1_Click(ByVal sender As System.Object, _
                              ByVal e As System.EventArgs) Handles Button1.Click

        Dim allowedCH As New System.Text.StringBuilder("`1234567890-=~!@#$&#37;^&*()_+qwertyuiop[]\QWERTYUIOP{}|asdfghjkl;'ASDFGHJKL:""zxcvbnm,./ZXCVBNM<>?")
        Dim newRandCharString As New System.Text.StringBuilder

        Stop
        'press F8 and use the debugger to gain understanding

        Do While allowedCH.Length > 0
            Dim idx As Integer = prng.Next(allowedCH.Length)
            newRandCharString.Append(allowedCH(idx))
            allowedCH.Remove(idx, 1)
        Loop
        Debug.WriteLine(newRandCharString.ToString)
    End Sub

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I am sorry to say this, but I have no idea what you are doing with the System.Text.StringBuilders.

The only thing I understand about it is: when allowed characters > 0 then it will 'Append' a StringBuilder.


I'd like some more information about this code, and if possible the full code. Thanks in advance!

Quote:

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Originally Posted by Teunjack

I am sorry to say this, but I have no idea what you are doing with the System.Text.StringBuilders.

The only thing I understand about it is: when allowed characters > 0 then it will 'Append' a StringBuilder.


I'd like some more information about this code, and if possible the full code. Thanks in advance!

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I edited my previous post so you could test the code. Here is a link to the documentation: http://msdn.microsoft.com/en-us/libr...ngbuilder.aspx

Sorry, but i'm having an error at the following line:

vb.net Code:

Dim idx As Integer = prng.Next(allowedCH.Length)

Error: System.NullReferenceException was unhandled. Object reference not set to an instance of an object.

I think i'll have to explain what I want better: I want to pick it a new char for the current char, and note the current char in RichTextBox1 and the new char after it, and after that add a VbCrlf/VbNewLine, so you'll get like some kind of 'encryption alphabet'.

I would greatly appreciate this code!

@dbas, what's "prng" in the code you posted? I can't find a declaration for it.

It's a random object, and the declaration is the very first line of his post.

@Teunjack: Did you get that "Private prng as New Random" line as DBas has?

@DBas: F8 is not going to work for all configurations of VS. For many of us, it is F10 and F11 that are used, instead.

ah, there it is. the browser scrolled down the "code block" and it was hidden.

Quote:

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Originally Posted by Shaggy Hiker

It's a random object, and the declaration is the very first line of his post.

@Teunjack: Did you get that "Private prng as New Random" line as DBas has?

@DBas: F8 is not going to work for all configurations of VS. For many of us, it is F10 and F11 that are used, instead.

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Did not know that shag, thanks.

Yet ANOTHER randomise question... at least this one has the decency to provide a different datatype than Integers :)

I'm also sensing a request to be able to pull characters from the randomised source, rather than just randomising the whole thing... since VB doesn't have iterator blocks yet, I did a poor man's Enumerable (I can't be faffed implementing IEnumerable and IEnumerator, so this'll do)

vbnet Code:

Public Class RandomCharacters
 
    Private ReadOnly m_allowedCharacters() As Char
    Private m_remainingCharacters As Integer
    Private ReadOnly m_random As System.Random
 
    Public Sub New(ByVal allowedCharacters As String, ByRef random As System.Random)
 
        m_allowedCharacters = allowedCharacters.ToCharArray
        m_remainingCharacters = m_allowedCharacters.Length
        m_random = random
 
    End Sub
 
    Public ReadOnly Property CharactersRemaining As Boolean
        Get
            Return m_remainingCharacters > 0
        End Get
    End Property
 
    Public Function GetNextCharacter() As Char
        If m_remainingCharacters < 1 Then
            Throw New InvalidOperationException("Cannot retrieve more characters from source")
        End If
 
        ' We are considering the characters in the range 0 -> # remaining characters
        ' Get a random element from within that range and store a copy of it to return
        ' at the end of this iteration
        Dim nextCharacterIndex As Integer = m_random.Next(m_remainingCharacters)
        Dim returnCharacter As Char = m_allowedCharacters(nextCharacterIndex)
 
        ' Place the last character from the range we are considering
        ' (will not be considered next time) into the place where we
        ' just got the character from.
        m_allowedCharacters(nextCharacterIndex) = m_allowedCharacters(m_remainingCharacters - 1)
 
        ' And now decrement the range that we will consider for the
        ' next iteration
        m_remainingCharacters = m_remainingCharacters - 1
 
        Return returnCharacter
 
    End Function
End Class

Usage:

vbnet Code:

Dim random As New System.Random
Dim allowedCharacters As String = "`1234567890-=~!@#$%^&*()_+qwertyuiop[]\QWERTYUIOP{}|asdfghjkl;'ASDFGHJKL:""zxcvbnm,./ZXCVBNM<>?"
Dim allowedCharacters2 As String = "abc"
 
For i = 1 To 10
    Dim randomCharacters As New RandomCharacters(allowedCharacters2, random)
 
    Do While randomCharacters.CharactersRemaining
        Console.Write(randomCharacters.GetNextCharacter)
    Loop
    Console.WriteLine()
Next

For an explanation of how this algorithm works, see a previous post.

Quote:

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Originally Posted by dbasnett

Did not know that shag, thanks.

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I learned it here. It has something to do with one of the option settings, but I forget which one. Something to make it key compatible with VB6.

I'm sorry but I still don't understand the source.

What I want is that I have a RichTextBox called RichTextBox1, which will get filled with this:
` -> j
1 -> ;
2 -> Z

What I mean by that is that every character will get a new random character which isn't used yet, I hope I explained better this time..

Code:

---

    Const allowedCH As String = "abcdefghijklmnopqrstuvwxyz1234567890"
    Dim prng As New Random
    Dim newRandCharString As New System.Text.StringBuilder

    Private Sub Button1_Click(ByVal sender As System.Object, _
                              ByVal e As System.EventArgs) Handles Button1.Click
        'get a new random character, and remove from list
        If newRandCharString.Length = 0 Then
            Debug.WriteLine("no more characters")
            Exit Sub
        End If
        Dim idx As Integer = prng.Next(newRandCharString.Length)
        RichTextBox1.AppendText(newRandCharString(idx) & Environment.NewLine)
        newRandCharString.Remove(idx, 1)
        RichTextBox1.ScrollToCaret()
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, _
                              ByVal e As System.EventArgs) Handles Button2.Click
        'restart
        RichTextBox1.Clear()
        newRandCharString.Length = 0
        newRandCharString.Append(allowedCH)
    End Sub

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