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Microsoft KB Archive/169617

From BetaArchive Wiki

Article ID: 169617

Article Last Modified on 8/30/2004



APPLIES TO

  • Microsoft Visual Basic 4.0 Enterprise Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • Microsoft Visual Basic 4.0 Professional Edition
  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic for Applications 5.0
  • Microsoft Visual Basic for Applications 6.0



This article was previously published under Q169617

SUMMARY

This article demonstrates how to use sort algorithms for sorting numeric arrays. It describes three methods of sorting a series of numbers and provides sample code that shows how to implement them with the time taken to sort by each algorithm.

MORE INFORMATION

It is often necessary to sort a series of numbers in code, and there are various sorting algorithms available to do this.

This article includes three methods:

  • Bubble sort
  • Selection sort
  • Shell sort

Each routine simply receives an array full of numbers within the bounds of a LONG datatype, although this could be easily changed for different numeric datatypes. Note that the sort routines return the result of the sort operation in the array that is passed to the routine. Therefore, if you do not want the original array to be modified, copy the array to a variant, as shown in the example below, and then pass the variant to the relevant procedure.

Step-by-Step Example

  1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.
  2. Place a CommandButton (Command1) onto Form1.
  3. Add the following code in the code window of Form1:

    Option Explicit
    
    Dim startTime As Double
    Dim endTime As Double
    Dim timeToSort As Double
    Dim timeTaken As String
    
    Sub Command1_Click()
      Dim lMyArray(0 To 2000) As Long
      Dim vTemp1 As Variant
      Dim vTemp2 As Variant
      Dim vTemp3 As Variant
      Dim iLoop As Integer
     
      Randomize
      For iLoop = LBound(lMyArray) To UBound(lMyArray)
        lMyArray(iLoop) = Int(Rnd * 100) + 1
      Next iLoop
      vTemp1 = lMyArray
      vTemp2 = lMyArray
      vTemp3 = lMyArray
      Screen.MousePointer = vbHourglass
      Call BubbleSortNumbers(vTemp1)
      Call SelectionSortNumbers(vTemp2)
      Call ShellSortNumbers(vTemp3)
      Screen.MousePointer = vbDefault
      MsgBox timeTaken
    End Sub
    
    Sub BubbleSortNumbers(iArray As Variant)
      Dim lLoop1 As Long
      Dim lLoop2 As Long
      Dim lTemp As Long
      
      startTime = Time()
      For lLoop1 = UBound(iArray) To LBound(iArray) Step -1
        For lLoop2 = LBound(iArray) + 1 To lLoop1
          If iArray(lLoop2 - 1) > iArray(lLoop2) Then
            lTemp = iArray(lLoop2 - 1)
            iArray(lLoop2 - 1) = iArray(lLoop2)
            iArray(lLoop2) = lTemp
          End If
        Next lLoop2
      Next lLoop1
      endTime = Time()
      timeToSort = endTime - startTime
      timeTaken = "Bubble Sort: " & timeToSort
    End Sub
    
    Sub SelectionSortNumbers(vArray As Variant)
      Dim lLoop1 As Long
      Dim lLoop2 As Long
      Dim lMin As Long
      Dim lTemp As Long
    
      startTime = Time()
      For lLoop1 = LBound(vArray) To UBound(vArray) - 1
        lMin = lLoop1
          For lLoop2 = lLoop1 + 1 To UBound(vArray)
            If vArray(lLoop2) < vArray(lMin) Then lMin = lLoop2
          Next lLoop2
          lTemp = vArray(lMin)
          vArray(lMin) = vArray(lLoop1)
          vArray(lLoop1) = lTemp
      Next lLoop1
      endTime = Time()
      timeToSort = endTime - startTime
      timeTaken = timeTaken & ";   Selection Sort: " & timeToSort
    End Sub
    
    Sub ShellSortNumbers(vArray As Variant)
      Dim lLoop1 As Long
      Dim lHold As Long
      Dim lHValue As Long
      Dim lTemp As Long
    
      startTime = Time()
      lHValue = LBound(vArray)
      Do
        lHValue = 3 * lHValue + 1
      Loop Until lHValue > UBound(vArray)
      Do
        lHValue = lHValue / 3
        For lLoop1 = lHValue + LBound(vArray) To UBound(vArray)
          lTemp = vArray(lLoop1)
          lHold = lLoop1
          Do While vArray(lHold - lHValue) > lTemp
            vArray(lHold) = vArray(lHold - lHValue)
            lHold = lHold - lHValue
            If lHold < lHValue Then Exit Do
          Loop
          vArray(lHold) = lTemp
        Next lLoop1
      Loop Until lHValue = LBound(vArray)
      endTime = Time()
      timeToSort = endTime - startTime
      timeTaken = timeTaken & ";   Shell Sort: " & timeToSort
    End Sub
                        
  4. Run the project, and click Command1. You receive the following output or similar:
    Bubble Sort: 4.6296E -05; Selection Sort: 3.4722E -05; Shell Sort: 0
                            

NOTE: In most cases, the Shell sort is the fastest of the three sorts presented. To determine which sort is faster, you can also use the QueryPerformanceCounter function to time the application code.

REFERENCES

For additional information on how to use the QueryPerformanceCounter function, click the article number below to view the article in the Microsoft Knowledge Base:

172338 How To Use QueryPerformanceCounter to Time Code


Keywords: kbhowto kbsample KB169617