CODEWITHSUNDEEP
vb.net
Anonymous
Anonymous

Reputation: 11

Remove elements from hashset of integer VB.Net

how do i make this work, does not work like a normal list. I have to delete from the list, which contains i.

if my list contains (2,4,3,13,21,14,15,30)

I want to delete the first 6 elemtent.

  Public randomcards As New HashSet(Of Integer)

        For i As Integer = 0 To 5
          randomcards.remove(i)
        Next

so after the operation, my list will become 15,30 with only 2 element.

Unfortunately, this is not a normal list and I would need a little help

Upvotes: 0

Views: 221

Answers (2)

Mary
Mary

Reputation: 15091

This is rather tedious because you can't refer to items in a HashSet by index. Keep in mind you can't alter any collection in a For Each by removing an element.

  1. Create a HashSet.

  2. Create a list.

  3. Add the first 6 elements of the HashSet to the list.

  4. Loop through the list checking if the item in the list is in the HashSet. If True remove it.

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim hs As New HashSet(Of Integer) From {2, 4, 3, 13, 21, 14, 15, 30}
    Dim lst As New List(Of Integer)
    Dim counter As Integer
    For Each i In hs
        If counter < 6 Then
            lst.Add(i)
        Else
            Exit For
        End If
        counter += 1
    Next
    For Each i In lst
        If hs.Contains(i) Then
            hs.Remove(i)
        End If
    Next
    MessageBox.Show(hs.Count.ToString)
    For Each i In hs
        Debug.Print(i.ToString)
    Next
End Sub


@Calaf's answer look superior.

Upvotes: 0

Calaf
Calaf

Reputation: 1173

By definition, an HashSet collection is not sorted (see the documentation), so

I want to delete the first 6 element

makes no sense.

If you know which element you want to remove (for example the number 14), use

randomcards.Remove(14)

By the same principle, if you want to remove 6 randomic integer (compliance with the insertion order is not guaranteed!), you can do something like this:

Dim fakeList As Integer() = randomcards.ToArray()
For i As Integer = 0 To 5
    randomcards.Remove(fakeList(i))
Next

Upvotes: 2

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