VBA copy cells from loop - vba

Question

I have a columns filled with string cells separated by spaces such as:
"abc def ghi jkl"
"abcde fghi jkl"
"abcdef ghijkl"
"abcdefghijkl"
My objectives are:
When there is four words I take each of the first letters of each word
When there is three words I take the first two letters of the first word and then each of the first letters of the following words
When there is two words I take the first two letters of each word
When there is only one word I take the first four letters
For each case I copy the resulting four letters found into another cell on the same row.
Being new to vba I didn't go very far. I started with Case 1 but it is incomplete and not returning anything:
Sub MyMacro()
Dim r As Range
Dim a, b, c, d, s As String
Dim v As Variant
Dim w As Worksheet
Set w = Worksheets("Sheet1")
w.Activate
Set r = w.Range("B1").End(xlDown).Rows
For Each v In r.Cells
If UBound(Split(v, " ")) = 3 Then
a = Left(Split(v, " ")(0), 1)
b = Left(Split(v, " ")(1), 1)
c = Left(Split(v, " ")(2), 1)
d = Left(Split(v, " ")(3), 1)
End If
Next
End Sub
Why aren't a, b, c and d not returning anything?
While I am looping through the cells of the range, how do I say that I want to copy the concatenated values of a, b, c and d into an adjacent cell?
Edited to replace "#" with " ".

Answer 1

Sub MyMacro()
Dim r As Range
Dim a, b, c, d, s As String
Dim v As Variant
Dim w As Worksheet
Dim arr, res
Set w = Worksheets("Sheet1")
w.Activate
Set r = w.Range(w.Range("B1"), w.Range("B1").End(xlDown))
For Each v In r.Cells
arr = Split(v.Value, " ")
select case ubound(arr)
case 0: res=left(arr(0),4)
case 1:'etc
case 2:'etc
case 3:'res = left(arr(0),1) & left(arr(1),1)'...etc
case else: res = "???"
End Select
v.offset(0,1).value=res
Next v
End Sub

Answer 2

Let's say your worksheet looks like this
Then try this
Option Explicit
Sub Sample()
Dim ws As Worksheet
Dim lRow As Long, i As Long, n As Long
Dim MyAr, sval
Set ws = ThisWorkbook.Sheets("Sheet1")
With ws
lRow = .Range("A" & .Rows.Count).End(xlUp).Row
For i = 1 To lRow
sval = .Range("A" & i).Value
If InStr(1, sval, " ") Then
MyAr = Split(sval, " ")
n = UBound(MyAr) + 1
Select Case n
Case 2:
.Range("B" & i).Value = Left(MyAr(0), 2) & Left(MyAr(1), 2)
Case 3
.Range("B" & i).Value = Left(MyAr(0), 2) & Left(MyAr(1), 1) & Left(MyAr(2), 1)
Case 4
.Range("B" & i).Value = Left(MyAr(0), 1) & Left(MyAr(1), 1) & _
Left(MyAr(2), 1) & Left(MyAr(3), 1)
End Select
Else
.Range("B" & i).Value = Left(sval, 4)
End If
Next i
End With
End Sub
Output