gaoxtwarrior
a sort which is stable means it keeps the object's original order. A sort
which is in place is stable. does anyone can explain me what is sort in
place?
thx.
Mar 29 '07 #1
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santosh
gaoxtwarrior wrote:
a sort which is stable means it keeps the object's original order. A sort
which is in place is stable. does anyone can explain me what is sort in
place?
It means no significant additional storage is used while sorting.
Mar 29 '07 #2
Malcolm McLean
"gaoxtwarri or" <ga***@cssweb.c om.cnwrote in message
>a sort which is stable means it keeps the object's original order. A sort
which is in place is stable. does anyone can explain me what is sort in
place?
Your premise is wrong. qsort() is an sort in place - if you print out the
array as it is sorting you will see values moving up and down within it -
but it is not stable. If Fred fred freddie and Freda all compare equal
because you are doing a case-insensitive comparision of the first four
letters, they will be contigous but in a random order when the sort
finished. A stable sort preserve the order of equal keys.
You can turn qsort into a stable sort by using the index as a tie breaker.
Mar 29 '07 #3
Eric Sosman
Malcolm McLean wrote On 03/29/07 15:28,:
"gaoxtwarri or" <ga***@cssweb.c om.cnwrote in message
>>a sort which is stable means it keeps the object's original order. A sort
which is in place is stable. does anyone can explain me what is sort in
place?
Your premise is wrong. qsort() is an sort in place - if you print out the
array as it is sorting you will see values moving up and down within it -
but it is not stable. If Fred fred freddie and Freda all compare equal
because you are doing a case-insensitive comparision of the first four
letters, they will be contigous but in a random order when the sort
finished. A stable sort preserve the order of equal keys.
You can turn qsort into a stable sort by using the index as a tie breaker.
Just to be clear: That's the "original" index, not the
index that the item happens to occupy at some random moment
during the sort.
--
Er*********@sun .com
Mar 29 '07 #4
Richard Harter
On Thu, 29 Mar 2007 20:28:35 +0100, "Malcolm McLean"
<re*******@btin ternet.comwrote :
>
"gaoxtwarrio r" <ga***@cssweb.c om.cnwrote in message>>a sort which is stable means it keeps the object's original order. A sortYour premise is wrong. qsort() is an sort in place - if you print out the
which is in place is stable. does anyone can explain me what is sort in
place?
array as it is sorting you will see values moving up and down within it -
but it is not stable. If Fred fred freddie and Freda all compare equal
because you are doing a case-insensitive comparision of the first four
letters, they will be contigous but in a random order when the sort
finished. A stable sort preserve the order of equal keys.
You can turn qsort into a stable sort by using the index as a tie breaker.
Your description applies to quicksort; IIANM qsort is a library routine
that can be implemented in any old way that the implementor feels like
using, including a stable sort.
>
Mar 29 '07 #5
Keith Thompson
"Malcolm McLean" <re*******@btin ternet.comwrite s:
"gaoxtwarri or" <ga***@cssweb.c om.cnwrote in message>a sort which is stable means it keeps the object's original order. AYour premise is wrong. qsort() is an sort in place - if you print out
sort which is in place is stable. does anyone can explain me what is
sort in place?
the array as it is sorting you will see values moving up and down
within it -
but it is not stable.
[...]
I think you're talking about the Quicksort algorithm. The C qsort()
function, declared in <stdlib.h>, may or may not use Quicksort; it's
allowed to use a either a stable or an unstable algorithm.
(I think there are also stable variants of Quicksort, but I don't know
the details.)
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
Mar 29 '07 #6
Richard Tobin
In article <ln************ @nuthaus.mib.or g>,
Keith Thompson <ks***@mib.orgw rote:
>>a sort which is stable means it keeps the object's original order. A
sort which is in place is stable. does anyone can explain me what is
sort in place?
>Your premise is wrong. qsort() is an sort in place - if you print out
the array as it is sorting you will see values moving up and down
within it -
but it is not stable.
>I think you're talking about the Quicksort algorithm. The C qsort()
function, declared in <stdlib.h>, may or may not use Quicksort; it's
allowed to use a either a stable or an unstable algorithm.
The other part is true though: qsort() does sort in place, as far as
the input and output are concerned. And qsort() is not guaranteed to
be stable, and isn't in many implementations , so it serves as an
example of an in-place sort which is not necessarily stable.
-- Richard
--
"Considerat ion shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.
Mar 29 '07 #7
lawrence.jones
santosh <sa*********@gm ail.comwrote:
gaoxtwarrior wrote:>a sort which is stable means it keeps the object's original order. A sort
which is in place is stable. does anyone can explain me what is sort in
place?
It means no significant additional storage is used while sorting.
Which means it has nothing to do with stability. An in-place sort need
not be stable. In fact, the standard library function qsort() is an
in-place sort, but it's not guaranteed to be stable and most
implementations are not.
-Larry Jones
It's not denial. I'm just very selective about the reality I accept.
-- Calvin
Mar 29 '07 #8
CBFalconer
santosh wrote:
gaoxtwarrior wrote:
>a sort which is stable means it keeps the object's original order.
A sort which is in place is stable. does anyone can explain me
what is sort in place?
It means no significant additional storage is used while sorting.
Nonsense on the stable. It means items which sort equal appear in
the original order.
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>
--
Posted via a free Usenet account from http://www.teranews.com
Mar 30 '07 #9
CBFalconer
Keith Thompson wrote:
>
.... snip ...
>
(I think there are also stable variants of Quicksort, but I don't know
know the details.)
I don't think so, without using auxiliary data (such as indices).
I am prepared to be proven wrong on this.
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>
--
Posted via a free Usenet account from http://www.teranews.com
Mar 30 '07 #10
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