Re: Shell sort for c#
From: Mike Kitchen (publicjoe_at_hotmail.com)
Date: 08/05/04
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Date: Thu, 5 Aug 2004 07:41:49 +0100
Hi Manju
I have a few sort routines on my site that you may wish to look at. These
are tried and tested, and ported from C.
They include a shell sort routine which can be found at the following link
http://www.publicjoe.f9.co.uk/csharp/sort07.html
Hope this helps
Publicjoe
C# Tutorial at http://www.publicjoe.f9.co.uk/csharp/tut.html
C# Snippets at http://www.publicjoe.f9.co.uk/csharp/snip/snippets.html
C# Ebook at http://www.publicjoe.f9.co.uk/csharp/samples/ebook.html
VB Ebook at http://www.publicjoe.f9.co.uk/vbnet/samples/ebook.html
"Majnu" <spam@majnu.net> wrote in message
news:5906a995.0408041228.4afa3822@posting.google.com...
> Hi community,
>
> just in case somebody needs a shellsort in c#, I rewrote the pascal
> code that I found in another newsgroup. Here are both. For more
> explanation on the pascal code you can search for the post on google.
>
> I was interested in the shell sort because I needed to sort long lists
> of data that may already be in order. For that reason I didn't want to
> use the arraylist's sort method, which uses quick sort (and has a
> worst case for lists that are already in order). However, I found out
> that the shell sort performs slower than the arraylist's sort method,
> even for ordered lists with 1000000 members. I guess this is because
> the sort method is hard wired into c#, but I'm not sure.
>
> Anyway, here it is:
>
> public static void shellSort(IList list, int first, int n, IComparer
> comparer)
> {
> int dummyRemainder; // not needed but required by System.Math.DivRem
> int incr = System.Math.DivRem((n * 10), 17, out dummyRemainder);
> int last = n - 1 + first;
>
> while(incr > 0)
> {
> for(int i = first; i <= (last - incr); i++)
> {
> int j = i;
> while((j >= first) &&
> (comparer.Compare(list[j], list[j + incr]) > 0))
> {
> listSwap(list, j, j + incr);
> j -= incr;
> }
> }
> incr = System.Math.DivRem((incr * 10), 17, out dummyRemainder);
> }
> }
>
> private static void listSwap(IList list, int i, int j)
> {
> object o = list[i];
> list[i] = list[j];
> list[j] = o;
> }
>
>
> Procedure ShellSort(first,n:integer;InOrder:CompareFunc;
> Swap:SwapProc);
> var i,j,incr,last:integer;
> Begin
> incr:=longint(n)*10 div 17;
> last:=n-1+first;
>
> while incr>0 do begin
> for i:=first to last-incr do begin
> j:=i;
> while (j>=first) and Not InOrder(j,j+incr) do begin { Short
> circuit! }
> Swap(j,j+Incr);
> dec(j,incr);
> End
> End;
> incr:=longint(incr)*10 div 17;
> End;
> End;
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