Question

I have a standard deck of 52 cards is represented in an array. Each card is represented as an integer. I wrote the below function to shuffle the cards. Does the code below look ok?

Module Module3

Sub Main()

    ' initialize array
    Dim Cards(52) As Integer

    ' Unit Test
    ' Pass array as argument.
    Console.WriteLine(shuffle(Cards))

End Sub

Function shuffle(ByVal Cards() As Integer)

    Dim counter = 1
    Dim rand = New Random()

    For Each card In Cards

        ' Grab random number with range of 52
        Dim n = rand.Next(52)

        ' Pick a card
        Dim temp = Cards(counter)

        ' Swap picked card with random card
        Cards(counter) = Cards(n)
        Cards(n) = temp

        counter += 1

    Next

    Return (Cards)

End Function

End Module

Answer 1

No, the code doesn’t do what you say.

Dim Cards(52) As Integer

This will create an array for 53 cards, not 52. Use:

Dim Cards(51) As Integer

When shuffling, swap each card with a card earlier in the deck (or itself), not anywhere in the deck. (This is the principle of the Fisher-Yates shuffle.)

Instead of having a counter separate from the loop, use the counter for the looping.

Dim rand = New Random()

For counter = 0 to Cards.Length - 1

  Dim n = rand.Next(counter + 1)

  Dim temp = Cards(counter)
  Cards(counter) = Cards(n)
  Cards(n) = temp

Next