edit dimension of array vba - arrays

Question

I have an array like this
dim arr(1 to 5) as string
arr(1)="a"
arr(3)="b"
arr(5) = "c"
(arr(2),arr(4) are empty).
How can I redim this arr(1to5) to exclude empty values and save also values "a","b","c" (I want the output like arr(1to3), arr(1)="a", arr(2)="b", arr(3)="c")?
In general I do not know how many of them will be empty, so I need some general code for this (not for this specific example).
I was thinking about new temporary array to save all nonempty values and then redim arr(1to5).
Maybe it is a better (quick) way to do it?
I wrote sth similar:
Sub test()
Dim myArray() As String
Dim i As Long
Dim y As Long
ReDim Preserve myArray(3)
myArray(1) = "a"
myArray(3) = "c"
Dim myArray2() As String
y = 1
For i = LBound(myArray) To UBound(myArray)
If myArray(i) <> "" Then
ReDim Preserve myArray2(y)
myArray2(y) = myArray(i)
y = y + 1
End If
Next i
ReDim myArray(UBound(myArray2))
myArray = myArray2
End Sub
However I would like to avoid creating new array.

Answer 1

create a new array of the same size. Loop the first array and insert the values when not empty into the new array keeping track of the last spot with value in the new array, then redim preserve the new array to only the size that has values.
Sub kjlkj()
Dim arr(1 To 5) As String
arr(1) = "a"
arr(3) = "b"
arr(5) = "c"
Dim newArr() As String
ReDim newArr(1 To UBound(arr))
Dim j As Long
j = LBound(newArr)
Dim i As Long
For i = LBound(arr) To UBound(arr)
If arr(i) <> "" Then
newArr(j) = arr(i)
j = j + 1
End If
Next i
ReDim Preserve newArr(LBound(newArr) To j - 1)
'do what you want with the new array.
End Sub

Answer 2

Alternative via Filter() function
"However I would like to avoid creating new array."
A negative filtering allows a basically simple alternative, however you have to
declare your array dynamically (i.e. without preset number of elements) to allow a rebuild overwriting the original array,
execute a double replacement over the joined array elements to allow insertion of a unique character that can be filtered out.
Sub testFilter()
Dim arr() As String
ReDim arr(1 To 5)
arr(1) = "a"
arr(3) = "b"
arr(5) = "c"
'Debug.Print Join(arr, ",") ' ~~> a,,b,,c
'rearrange arr via RemoveEmpty()
arr = RemoveEmpty(arr) ' >> function RemoveEmpty()
Debug.Print Join(arr, ",") ' ~~> a,b,c
End Sub
Help function RemoveEmpty()
Adding an unused unique character, e.g. $, to the empty elements plus eventual negative filtering allows to remove these marked elements.
Note that the double replacement is necessary to allow to mark consecutive empty elements by the $ mark, as VBA would skip additional characters here.
Function RemoveEmpty(arr)
Dim tmp
tmp = Replace(Replace(Join(arr, "|"), "||", "|$|"), "||", "|$|")
RemoveEmpty = Filter(Split(tmp, "|"), "$", False)
End Function