Vb.net all combinations

Question

I have 6 items which have to be combinated,

items listed: ( this is an example)

• Ape
• Cow
• Deer | Small deer | Big deer

Answer 1

Here's a recursive solution for VB 2010 (probably not very good performance-wise when there are a lot of combinations, but it's a start):

Function GetCombinations(items As String()(), Optional index As Integer = 0) As List(Of String())
    Dim combinations As New List(Of String())
    Dim lastIndex = items.Count - 1
    Select Case index
        Case Is < 0, Is > lastIndex
            Throw New ArgumentException("index should be 0 or greater")
        Case lastIndex
            For Each item In items(index)
                combinations.Add({item})
            Next
        Case Else
            Dim nextCombinations = GetCombinations(items, index + 1)
            For Each item In items(index)
                For Each nextCombination In nextCombinations
                    combinations.Add({item}.Concat(nextCombination).ToArray)
                Next
            Next
    End Select
    Return combinations
End Function

Test code:

Dim items = {({"Ape"}), ({"Cow"}), ({"Deer", "Small deer", "Big deer"}), ({"Sheep"}), ({"Mouse", "Black Mouse", "White mouse"})}
For Each combination In GetCombinations(items)
    Console.WriteLine(String.Join(", ", combination))
Next

Test outputs:

Ape, Cow, Deer, Sheep, Mouse
Ape, Cow, Deer, Sheep, Black Mouse
Ape, Cow, Deer, Sheep, White mouse
Ape, Cow, Small deer, Sheep, Mouse
Ape, Cow, Small deer, Sheep, Black Mouse
Ape, Cow, Small deer, Sheep, White mouse
Ape, Cow, Big deer, Sheep, Mouse
Ape, Cow, Big deer, Sheep, Black Mouse
Ape, Cow, Big deer, Sheep, White mouse