Problems when shuffling an array of strings

Question

I am attempting to shuffle an array of strings, below is the segment of code i have already. However, a problem with this code is that alot of the times it shuffles the content but excludes one value. e.g shuffling A, B, C, D it will do this: A, D , , C.

Any help would be greatly appreciated.

Private rnd = New Random()

Public Sub Shuffle(ByRef List() As String)
    Dim Limit As Integer = List.Length - 1

    For i = Limit To 0 Step -1
        Dim j As Integer = rnd.Next(0, i + 1)
        Dim temp As String = List(i)
        List(i) = List(j)
        List(j) = temp
    Next
End Sub

Dim j As Integer = rnd.Next(0, Limit + 1) not sure if it is related but you want to make sure each element is considered for swap at least once — Ňɏssa Pøngjǣrdenlarp
– Ňɏssa Pøngjǣrdenlarp, Commented Oct 28, 2015 at 19:06
You are not providing enough information (= original values in List), but your problem has most likely to do with the fact that the list contains a blank value which is being included in the shuffling. — user2480047
– user2480047, Commented Oct 28, 2015 at 19:11
Cannot reproduce - 500 reps and nothing was skipped/dropped. Make sure you dont have any empties in your array — Ňɏssa Pøngjǣrdenlarp
– Ňɏssa Pøngjǣrdenlarp, Commented Oct 28, 2015 at 19:24

Reza Aghaei · Accepted Answer · 2015-10-28 19:36:24Z

1

As a simple and clean option you can shuffle a list of string this way:

Public Function Shuffle(source As List(Of String)) As List(Of String)
    Dim rnd = New Random(System.DateTime.Now.Millisecond)
    Return source.OrderBy(Function(item) rnd.Next()).ToList()
End Function

And here is the usage:

Dim list = New List(Of String) From {"A", "B", "C", "D"}
Dim result = Shuffle(list)
MessageBox.Show(String.Join("," , result))

edited Oct 28, 2015 at 19:36

answered Oct 28, 2015 at 19:12

Reza Aghaei

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