Microsoft KB Archive/169617

= How To Sort Algorithms for Numeric Arrays =

Article ID: 169617

Article Last Modified on 8/30/2004

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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

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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
 Start a new Standard EXE project in Visual Basic. Form1 is created by default. Place a CommandButton (Command1) onto Form1.  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  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.

