CodeSnip: Simple Array Shuffler: ASP Alliance


CodeSnip: Simple Array Shuffler

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by Joseph Chahine
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Introduction

ShuffleArray is a function that takes an array as argument, shuffles it, and returns another array holding the shuffled items.

Steps

The steps of shuffling are as follows:

1. Create a new array with the same dimension of the original array to be shuffled.

2. Select an item randomly from the original array and insert it in the new array.

3. Repeat the previous step until all items of the original array are copied to the new array.

4. Return the new array.

Code

The example given below demonstrates how to implement the above mentioned functionality.

Listing 1

Imports System.Security.Cryptography
 
Public Class ArrayUtilities
 
    Private Random As RNGCryptoServiceProvider = New RNGCryptoServiceProvider
    Private Bytes(4) As Byte
 
 
    Public Function ShuffleArray(ByVal argArr As Array) As Array
        Dim arr1 As New ArrayList(argArr)
 
  '' Creating an array of Objects having the same dimension as the argument Array.
        Dim arr2 As Array = Array.CreateInstance(GetType(Object), arr1.Count)
 
        Dim intIndex As Integer
 
        For i As Integer = 0 To arr1.Count - 1
            '' intIndex is a random number between 0 and arr1.Count-1
            intIndex = GenerateRandomNumber(arr1.Count)
            arr2(i) = arr1(intIndex)
            arr1.RemoveAt(intIndex)
        Next
 
        arr1 = Nothing
 
        Return arr2
    End Function
 
 
    Private Function GenerateRandomNumber(ByVal argMax As Integer) As Integer
        If argMax <= 0 Then Throw New Exception
        Random.GetBytes(Bytes)
        Dim intValue As Integer = (BitConverter.ToInt32(Bytes, 0)) Mod argMax
        If intValue < 0 Then intValue = -intValue
        Return intValue
    End Function
 
End Class
 
Module TestModule
 
    Sub Main()
        Dim AU As ArrayUtilities
        AU = New ArrayUtilities
 
        Dim OriginalArray As Integer() = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
        Dim ShuffledArray As Array = AU.ShuffleArray(OriginalArray)
 
        Dim i As Integer
        Dim stb As New System.Text.StringBuilder
 
        stb.Append("OriginalArray = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}")
        stb.Append(vbCrLf)
        stb.Append("ShuffledArray = {")
 
        For i = 0 To ShuffledArray.Length - 2
            stb.Append(ShuffledArray(i).ToString)
            stb.Append(", ")
        Next
 
        stb.Append(ShuffledArray(ShuffledArray.Length - 1).ToString)
        stb.Append("}")
 
        Console.Write(stb.ToString)
        Console.Read()
    End Sub
End Module

Analysis

In order to view the result of the above snippet, you should open and execute the Visual Studio 2005 project, which can be downloaded from the link given in the Downloads section. The final output will look like the figure below.

Figure 1

Downloads

[Download Source]

Summary

In this article you have learned how to shuffle an Array programmatically using Visual Basic 2005.

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