Sorting using an index number - vb.net

Question

How do i implement a index based sort in vb.net
Could someone guide me. By giving me a head start
eg
array = 9 8 7 6 5 4 3 2 1
Index Number = 5
Counting from 9 and the 5th character is 5.
So the first sorted character is 5.
Remove 5 and remains 9 8 7 6 4 3 2 1
start value should be from 4(current 5th character) now 5th character is 9 since it's circular
unsorted array : 8 7 6 4 3 2 1
sorted array : 5 9
any hints

Answer 1

First off, I definitely wouldn't call this "sorting"; it's a bit more like deterministically (non-randomly) "shuffling" the array. But I'll take a stab at this…
Basically, start by using List(Of T) rather than arrays, because they allow you to easily and remove at any point in the list, rather than arrays which are a fixed size. Next, use a running counter to track your current position in the input list, and use the Mod operator to make the index effectively 'wrap' around the end of the list. Use a While loop to continue until all the items from the input have been processed. It should look something like this:
Dim input As New List(Of Integer) From { 9, 8, 7, 6, 5, 4, 3, 2, 1 }
Dim stepBy As Integer = 5
Dim index As Integer = 0
Dim output As New List(Of Integer)
While input.Count > 0
index = (index + stepBy - 1) Mod input.Count
output.Add(input(index))
input.RemoveAt(index)
End While
In this case the output is:
5, 9, 3, 6, 7, 4, 1, 8, 2

Answer 2

I thought this was an interesting question and I loved the answer by p.s.w.g....
...but I was curious to see if any of the built-in .Net collections would facilitate a fairly trivial circular list.
This is what I came up with using the LinkedList class:
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim originalIntegers() As Integer = {9, 8, 7, 6, 5, 4, 3, 2, 1}
Dim output As New List(Of Integer)
Dim circleInts As New CircularIntegerList(originalIntegers)
circleInts.MoveForward(4) ' move forward 4 from the 1st to get the 5th slot
While circleInts.Count > 0
If circleInts.Current.HasValue Then
output.Add(circleInts.Current)
End If
circleInts.RemoveCurrent() ' next number in sequence becomes the current one
circleInts.MoveForward(4) ' move forward another 4, net jump is 5 from the deleted one
End While
Dim result As String = String.Join(",", output.Select(Function(x) x.ToString).ToArray)
Debug.Print(result)
End Sub
End Class
Public Class CircularIntegerList
Private values As New LinkedList(Of Integer)
Private _current As LinkedListNode(Of Integer)
Public Sub New(ByVal data() As Integer)
If data.Length > 0 Then
values = New LinkedList(Of Integer)(data)
_current = values.First
End If
End Sub
Public ReadOnly Property Current As Integer?
Get
If Not IsNothing(_current) Then
Return _current.Value
Else
Return Nothing
End If
End Get
End Property
Public ReadOnly Property Count As Integer
Get
Return values.Count
End Get
End Property
Public Sub RemoveCurrent()
If Not IsNothing(_current) Then
Dim tmp As LinkedListNode(Of Integer) = If(IsNothing(_current.Next), values.First, _current.Next)
values.Remove(_current)
If values.Count > 0 Then
_current = tmp
Else
_current = Nothing
End If
End If
End Sub
Public Sub MoveForward(Optional ByVal NumberOfJumps As Integer = 1)
If Not IsNothing(_current) Then
For i As Integer = 1 To NumberOfJumps
_current = If(IsNothing(_current.Next), values.First, _current.Next)
Next
End If
End Sub
End Class