Quick Sort

Quick Sort uses a 'divide and conquer' strategy to divide a list into two sub-lists.

Sub TestSort() 
Dim avTesting() As Variant 
   avTesting = Array(45, 30, 25, 15, 10, 5, 40, 20, 35, 50) 
   Call Array_QuickSort(avTesting) 
   Stop 
End Sub 

Public Sub Array_QuickSort(ByRef vArrayName As Variant, _ 
                  Optional ByVal lLower As Long = -1, _ 
                  Optional ByVal lUpper As Long = -1) 
                  
Dim vmiddlevalue As Variant 
Dim lmiddle As Long 
Dim lrowlower As Long 
Dim lrowupper As Long 
Dim stemp As String 

   If IsEmpty(vArrayName) = True Then Exit Sub 
   If lLower = -1 Then lLower = LBound(vArrayName, 1) 
   If lUpper = -1 Then lUpper = UBound(vArrayName, 1) 

   If lLower < lUpper Then 

      'lmiddle = lLower
      lmiddle = (lLower + lUpper) / 2 
      'lmiddle = VBA.Int(lLower + VBA.Rnd * (lUpper - lLower + 1))

      vmiddlevalue = vArrayName(lmiddle) 
      lrowlower = lLower 
      lrowupper = lUpper 
                        
      Do While lrowlower < lrowupper 
         Do While (vArrayName(lrowupper) >= vmiddlevalue) And (lrowlower < lrowupper) 
            lrowupper = lrowupper - 1 
         Loop 
         If (lrowlower <> lrowupper) Then 
            stemp = vArrayName(lrowlower) 
            vArrayName(lrowlower) = vArrayName(lrowupper) 
            vArrayName(lrowupper) = stemp 
            lrowlower = lrowlower + 1 
         End If 
         
         Do While (vArrayName(lrowlower) <= vmiddlevalue) And (lrowlower < lrowupper) 
            lrowlower = lrowlower + 1 
         Loop 
         If (lrowlower <> lrowupper) Then 
            stemp = vArrayName(lrowupper) 
            vArrayName(lrowupper) = vArrayName(lrowlower) 
            vArrayName(lrowlower) = stemp 
            lrowupper = lrowupper - 1 
         End If 
      Loop 
            
      vArrayName(lrowlower) = vmiddlevalue 
      lmiddle = lrowlower 
      lrowlower = lLower 
      lrowupper = lUpper 
      
      If (lrowlower < lmiddle) Then 
         Call Array_QuickSort(vArrayName, lrowlower, lmiddle - 1) 
      End If 
      If (lrowupper > lmiddle) Then 
         Call Array_QuickSort(vArrayName, lmiddle + 1, lrowupper) 
      End If 
   End If 
End Sub