Comments on: Bubble Sorts

By: fzz

fzz — Wed, 07 Jan 2009 20:51:00 +0000

My post with a quicksort procedure hasn't shown up, so I'll try again. Note: using FORTRAN-like comparison operators to eliminate the hassles with angle brackets.

Sub qsort( _
v As Variant, _
lft As Long, _
rgt As Long, _
Optional asc As Boolean = True _
)
'--------------------------------
'assumes simple 1D arrays
'defaults to ascending sort
'--------------------------------
Dim j As Long, pvt As Long, t As Variant

If lft .GE. rgt Then Exit Sub

j = lft + Int((rgt - lft + 1) * Rnd)
t = v(lft)
v(lft) = v(j)
v(j) = t

pvt = lft

For j = lft + 1 To rgt
If IIf(asc, v(j) .LT. v(lft), v(j) .GT. v(lft)) Then
pvt = pvt + 1
t = v(pvt)
v(pvt) = v(j)
v(j) = t
End If
Next j

t = v(lft)
v(lft) = v(pvt)
v(pvt) = t

qsort v, lft, pvt - 1, asc
qsort v, pvt + 1, rgt, asc
End Sub

By: Michael

Michael — Sat, 03 Jan 2009 05:57:00 +0000

OK...ok...I'll redo #29 with a quicksort and post it in a few days. Here's a reference on all kinds of sorts (quick/heap/shaker etc) with code:

http://69.20.37.124/showthread.php?p=403676

From the folks over at Xtreme Visual Basic.

You guys sound like my old CS profs...;-)

...mrt

By: dbb

dbb — Sat, 03 Jan 2009 01:17:00 +0000

Michael, quicksort code is also short, but it runs up to 200x as fast as bubblesort.

I sorted 10,000 random (long) numbers in 0.03 seconds vs 6 seconds with bubblesort.

By: Mike Woodhouse

Mike Woodhouse — Sat, 03 Jan 2009 01:06:00 +0000

Bubble sort. Ugh. As wikipedia says, "While simple, this algorithm is highly inefficient and is rarely used except in education"

I'll readily agree that it works, but surely we should make some room to attempt to produce a little elegance? Any of the algortihms that is O(n log n) for time and O(1) for memory (I get nervous about the stack for highly recursive sorts) would do. Heapsort isn't hard to implement in VBA (I'm sure I have one somewhere).