Qsort Not Working

[meanoscar47]

I got the below sort routine here years ago and it works great for sorting runner information...when all the Bib Numbers are unique.  I set up a test file to read in and sort 1500 bib numbers many of which are NOT unique.  It executes but excludes lower numbers generally.  My simple swapping code takes 25 seconds to execute and this one (doing it wrong however) is in the blink of an eye.  Will several dupes fool it?  Is there something inbetween simple swapping and this that will work?

call QSort 1, index



   goto [aftersort]



   sub QSort Start, Finish

   i = Start

   j = Finish

   x = Bib(int((i+j)/2))

   while i <= j

       while Bib(i) < x

       i = i + 1

   wend



   while Bib(j) > x

       j = j - 1

   wend

       if i <= j then

       a = Bib(i)      : b$ = NeTime$(i)         : c = Place(i)

       Bib(j) = Bib(i) : NeTime$(j) = NeTime$(i) : Place(j) = Place(i)

       Bib(j) = a      : NeTime$(j) = b$         : Place(j) = c

       i = i + 1

       j = j - 1

       end if

   wend



   if j > Start then call QSort Start, j

   if i < Finish then call QSort i, Finish

   end sub

   [aftersort]

Attachments:

192.168.1.30_read_summary.csv (209.5 KB)

[Brandon Parker]

Here is a short example of Quick Sort implemented in LB.

'Use a dedicated array for sorting
Dim QSortDataArray(99)

'Let's put some pseudo-random numbers into the array
For i = 0 To 99
   QSortDataArray(i) = Int(rnd(1) * 500) + 1
Next i

'Call the quickSort subroutine to sort the
'QSortDataArray() array
Call quickSort 0, 99

'Print the QSortDataArray() array out to show
'that we have sorted it
For i = 0 To 99
   Print QSortDataArray(i)
Next i

Wait


Sub quickSort minElement, maxElement
   If (minElement < maxElement) Then
       'pivotIndex is partitioning index, QSortDataArray(pivotIndex
       'is now at correct place in sorted array
       pivotIndex = partition(minElement, maxElement)

       Call quickSort minElement, (pivotIndex - 1)   'Before pivot_index
       Call quickSort (pivotIndex + 1), maxElement   'After pivot_index
   End If
End Sub

Sub swap elementA, elementB
   temp = QSortDataArray(elementA)
   QSortDataArray(elementA) = QSortDataArray(elementB)
   QSortDataArray(elementB) = temp
End Sub

Function partition(minElement, maxElement)
   'Selecting the last element as the pivot point
   pivotElement = QSortDataArray(maxElement)
   'Index of the smaller element
   partition = (minElement - 1)

   For i = minElement To (maxElement - 1)
       'If the current element is smaller than or equal to pivot
       If (QSortDataArray(i) <= pivotElement) Then
           'Increment the index of the smaller element
           partition = (partition + 1)
           'Do some swapping
           Call swap partition, i
       End If
   Next i
   'Do some swapping
   Call swap (partition + 1), maxElement
   partition = (partition + 1)
End Function


{:0)

Brandon Parker

[meanoscar47]

IN the second line of swapping, I had Bib(j) = Bib(i). Reversed, it works fine.

[Rod]

Coding your own is fun but Liberty has a built in Sort command which is much faster than a coded sort.