VBA: adding distinct values in a range to a new range - vba

Question

I have an unsorted list of names in Sheet1, Column A. Many of these names appear more than once in the list.
On Sheet2 Column A I want an alphabetically sorted list of the names with no duplicate values.
What is the optimal method of achieving this using VBA?
Methods I have seen so far include:
Making a collection with CStr(name) as the key, looping through the range and trying to add each name; if there is an error it is not unique, ignore it, else expand the range by 1 cell and add the name
Same as (1), except ignore about the errors. When the loop is complete, only unique values will be in the collection: THEN add the whole collection to the range
Using the match worksheet function on the range: if no match, expand the range by one cell and add the name
Maybe some simulation of the "remove duplicates" button on the data tab? (haven't looked into this)

Answer 1

I really like the dictionary object in VBA. It's not natively available but it's very capable. You need to add a reference to Microsoft Scripting Runtime then you can do something like this:
Dim dic As Dictionary
Set dic = New Dictionary
Dim srcRng As Range
Dim lastRow As Integer
Dim ws As Worksheet
Set ws = Sheets("Sheet1")
lastRow = ws.Cells(1, 1).End(xlDown).Row
Set srcRng = ws.Range(ws.Cells(1, 1), ws.Cells(lastRow, 1))
Dim cell As Range
For Each cell In srcRng
If Not dic.Exists(cell.Value) Then
dic.Add cell.Value, cell.Value 'key, value
End If
Next cell
Set ws = Sheets("Sheet2")
Dim destRow As Integer
destRow = 1
Dim entry As Variant
'the Transpose function is essential otherwise the first key is repeated in the vertically oriented range
ws.Range(ws.Cells(destRow, 1), ws.Cells(dic.Count, 1)) = Application.Transpose(dic.Items)

Answer 2

As you suggested, a dictionary of some sort is the key. I would use a Collection - it is builtin (in contrary to Scripting.Dictionary) and does the job.
If by "optimal" you mean "fast", the second trick is to not access each cell individually. Instead use a buffer. The below code will be fast even with thousands of rows of input.
Code:
' src is the range to scan. It must be a single rectangular range (no multiselect).
' dst gives the offset where to paste. Should be a single cell.
' Pasted values will have shape N rows x 1 column, with unknown N.
' src and dst can be in different Worksheets or Workbooks.
Public Sub unique(src As Range, dst As Range)
Dim cl As Collection
Dim buf_in() As Variant
Dim buf_out() As Variant
Dim val As Variant
Dim i As Long
' It is good practice to catch special cases.
If src.Cells.Count = 1 Then
dst.Value = src.Value ' ...which is not an array for a single cell
Exit Sub
End If
' read all values at once
buf_in = src.Value
Set cl = New Collection
' Skip all already-present or invalid values
On Error Resume Next
For Each val In buf_in
cl.Add val, CStr(val)
Next
On Error GoTo 0
' transfer into output buffer
ReDim buf_out(1 To cl.Count, 1 To 1)
For i = 1 To cl.Count
buf_out(i, 1) = cl(i)
Next
' write all values at once
dst.Resize(cl.Count, 1).Value = buf_out
End Sub