[RESOLVED] Keep last 10 numbers in List.

[thegreatone]

Hello, i want to keep only the last 10 numbers in a List.

The list is declared as:
Dim LastPlayed As New List(Of Integer)

I then Add several Items, each time checking LastPlayed.Count is no bigger than 10.
If it is, i only want to keep the 10 most recent numbers.

How would i do this?
It's been driving me nuts.

[ForumAccount]

How about a Queue(Of Integer)?

Dim queue As New Queue(Of Integer)
        With queue
            .Enqueue(10)
            .Enqueue(32)
            .Enqueue(3523)
            .Enqueue(324)
            .Enqueue(124)
            .Enqueue(53)
            .Enqueue(51)
            .Enqueue(5512)
            .Enqueue(214)
            .Enqueue(98)
        End With
        If queue.Count >= 10 Then
            queue.Dequeue() 'removes the first one that went in which is 10
            queue.Enqueue(18) 'the new integer
        End If

Everytime the count gets to 10, it dequeues the next first one that went in. (Always index 0)

[thegreatone]

How about a Queue(Of Integer)?

Dim queue As New Queue(Of Integer)
        With queue
            .Enqueue(10)
            .Enqueue(32)
            .Enqueue(3523)
            .Enqueue(324)
            .Enqueue(124)
            .Enqueue(53)
            .Enqueue(51)
            .Enqueue(5512)
            .Enqueue(214)
            .Enqueue(98)
        End With
        If queue.Count >= 10 Then
            queue.Dequeue() 'removes the first one that went in which is 10
            queue.Enqueue(18) 'the new integer
        End If

Everytime the count gets to 10, it dequeues the next first one that went in. (Always index 0)

I didn't even know .Net had this feature.

Fantastic stuff. This is exactly what i am looking for.

[ForumAccount]

I didn't even know .Net had this feature

Oh man, I don't know how many time's I've said that to myself.

[thegreatone]

After all this i realised i needed a FILO system, not FIFO. Eeek!

Useful thing though is Queue.
Shame i ended up using the original thing i posted about in the end.

It's always good to learn new things though!

[ForumAccount]

I thought you wanted the FIFO system sorry. The FILO equivalent is Stack(Of T):

Dim stack As New Stack(Of Integer)
        With stack
            .Push(1239)
            .Push(32)
            .Push(3523)
            .Push(324)
            .Push(124)
            .Push(53)
            .Push(51)
            .Push(5512)
            .Push(214)
            .Push(98)
        End With
        If stack.Count > 9 Then
            stack.Pop() 'removes last item to go in, the 98
            stack.Push(18) 'the new integer
        End If

Works the same way, except it removes the last item that went in when you call .Pop()

[thegreatone]

I thought you wanted the FIFO system sorry. The FILO equivalent is Stack(Of T):

Dim stack As New Stack(Of Integer)
        With stack
            .Push(1239)
            .Push(32)
            .Push(3523)
            .Push(324)
            .Push(124)
            .Push(53)
            .Push(51)
            .Push(5512)
            .Push(214)
            .Push(98)
        End With
        If stack.Count > 9 Then
            stack.Pop() 'removes last item to go in, the 98
            stack.Push(18) 'the new integer
        End If

Works the same way, except it removes the last item that went in when you call .Pop()

Jesus, it really does have everything built in these days...

Thankyou so very much! I Can't give you any more rep, but you deserve it.

[jmcilhinney]

The only drawback with using a Queue is that you can't access any item other than the next in the queue. Also, . If that's the functionality you want then that's great, but otherwise you should use a List.

Also, given that you're using a fully OOP language, why don't you take advantage of it by creating your own class to manage this? If you want FIFO functionality then make use of a Queue:

Public Class SizeLimitedQueue(Of T)
 
    Private maxSize As Integer
    Private items As Queue(Of T)
 
    Public ReadOnly Property Size() As Integer
        Get
            Return Me.items.Count
        End Get
    End Property
 
    Public Sub New(ByVal maxSize As Integer)
        Me.maxSize = maxSize
        Me.items = New Queue(Of T)(maxSize)
    End Sub
 
    Public Sub Add(ByVal item As T)
        If Me.items.Count = Me.maxSize Then
            Me.RemoveNext()
        End If
 
        Me.items.Enqueue(item)
    End Sub
 
    Public Function GetNext() As T
        Return Me.items.Peek()
    End Function
 
    Public Function RemoveNext() As T
        Return Me.items.Dequeue()
    End Function
 
    Public Function Swap(ByVal item As T) As T
        Dim result As T = Me.RemoveNext()
 
        Me.Add(item)
 
        Return result
    End Function
 
End Class

Now you can just do this:

Dim numbers As New SizeLimitedQueue(Of Integer)(10)

You can then just call Add and/or Swap as you like without ever having to worry about maintaining the size yourself. If you need random access to the items then you can do something similar with a List. You could also incorporate sorting internally to maintain a high score list or the like.