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Featured Discussion: Two Different Ways to Sort Arrays in VBScript

There are often many ways to solve a programming problem, and the problem of sorting multi-dimensional arrays is no exception. This featured discussion discusses two methods of solving the same sorting problem. First, how to sort a multi-dimensional array directly, and second, how to sort the same data placed in a user-defined type (UDT).


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om Gow is working on a Web page in ASP/VBScript. He's having trouble alphabetically sorting an array with state names. The array in question is loaded with the results of three different queries. The sort is working, but after it's complete, the data in three of the array columns is out of sync. How does he keep all of the rows of data in sync?

Solution #1
Larry Serflaten says the problem is that every time you move one item, you have to move every item in a whole row. However, this works for only small arrays—and thus, only with short rows. If the arrays are larger, with several items in a single row, it's undesirable to move that much data around—if it can be avoided.



One way to avoid this is to use a different array as a pointer (indexing) into the data array. This sorts the data, without having to move it, but it needs to be accessed through the indexing array.

Here's Larry's example code:

HTH KFS Private Sub Form_Load() Dim Data(0 To 1, 0 To 5) Dim I, J, Index Randomize Debug.Print "Original list:" For i = 0 To 5 J = Int(Rnd * 1000) Data(0, i) = J Data(1, i) = "ITEM" & Str(J) Debug.Print Data(0, i), Data(1, i) Next Sort Data, Index Debug.Print "Sorted:" For i = 0 To 5 Debug.Print Data(0, Index(i)), Data(1, Index(i)), "was: "; Data(0, i) Next End Sub Sub Sort(ByVal Data, ByRef Index) Dim p1, p2, pp ReDim Index(0 To 5) ' Hard coded for demo convenience For p2 = 0 To 5 Index(p2) = p2 Next p2 = 1 Do While p1 < 5 Select Case Sgn(Data(0, Index(p2)) - Data(0, Index(p1))) Case -1 pp = Index(p1) Index(p1) = Index(p2) Index(p2) = pp p2 = p1 + 1 Case 0, 1 p2 = p2 + 1 If p2 > 5 Then p1 = p1 + 1 p2 = p1 + 1 End If End Select Loop End Sub



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