September Morn Update

Task/Find-common-directory-path/Visual-Basic/find-common-directory-path.vb

@@ -0,0 +1,60 @@
+Public Function CommonDirectoryPath(ParamArray Paths()) As String
+Dim v As Variant
+Dim Path() As String, s As String
+Dim i As Long, j As Long, k As Long
+Const PATH_SEPARATOR As String = "/"
+
+  For Each v In Paths
+    ReDim Preserve Path(0 To i)
+    Path(i) = v
+    i = i + 1
+  Next v
+
+  k = 1
+
+  Do
+    For i = 0 To UBound(Path)
+      If i Then
+        If InStr(k, Path(i), PATH_SEPARATOR) <> j Then
+          Exit Do
+        ElseIf Left$(Path(i), j) <> Left$(Path(0), j) Then
+          Exit Do
+        End If
+      Else
+        j = InStr(k, Path(i), PATH_SEPARATOR)
+        If j = 0 Then
+          Exit Do
+        End If
+      End If
+    Next i
+    s = Left$(Path(0), j + CLng(k <> 1))
+    k = j + 1
+  Loop
+  CommonDirectoryPath = s
+
+End Function
+
+Sub Main()
+
+' testing the above function
+
+Debug.Assert CommonDirectoryPath( _
+ "/home/user1/tmp/coverage/test", _
+ "/home/user1/tmp/covert/operator", _
+ "/home/user1/tmp/coven/members") = _
+ "/home/user1/tmp"
+
+ Debug.Assert CommonDirectoryPath( _
+ "/home/user1/tmp/coverage/test", _
+ "/home/user1/tmp/covert/operator", _
+ "/home/user1/tmp/coven/members", _
+ "/home/user1/abc/coven/members") = _
+ "/home/user1"
+
+Debug.Assert CommonDirectoryPath( _
+ "/home/user1/tmp/coverage/test", _
+ "/hope/user1/tmp/covert/operator", _
+ "/home/user1/tmp/coven/members") = _
+ "/"
+
+End Sub