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Groups > comp.lang.python > #28615
| Date | 2012-09-06 11:54 -0400 |
|---|---|
| From | Dave Angel <d@davea.name> |
| Subject | Re: Comparing strings from the back? |
| References | (9 earlier) <mailman.272.1346885254.27098.python-list@python.org> <50485fca$0$29977$c3e8da3$5496439d@news.astraweb.com> <k2a99e$i5p$1@news.albasani.net> <mailman.304.1346941450.27098.python-list@python.org> <k2acou$p8n$1@news.albasani.net> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.313.1346946924.27098.python-list@python.org> (permalink) |
On 09/06/2012 10:42 AM, Johannes Bauer wrote: > On 06.09.2012 16:23, Dave Angel wrote: >> On 09/06/2012 09:43 AM, Johannes Bauer wrote: >>> <snip> >>> Yes, worst-case is O(N), best case O(1). Average is O(n log n). >> Can't see how you came up with an average of n log(n). Fourteen minutes >> before you made this post, you demonstrated it was less than 2 for any N. >> >> And I previously posted that for a character set of size 10, the average >> was 1.1111 > Again playing with the equations and thinking about it again. And I > completely missed your point. It wasn't about n log n vs. log n. Both > are wrong. This surprises me. I was somehow thinking about the limit of > sum (1/n), n -> infty. But since the summands are shrinking > exponentially, the limit is different. > > I think the limit of the average comparisons for a given wordlength n > against infinity with alphabet size l is > > l / (l - 1) > > i.e. for bitstrings it's 2 and for bytestrings it's 256/255. > > This would mean string comparison of randomized strings is O(1). Can > that really be true? It looks like it. > (Just lost the internet in a storm, so I'm not sure how long it'll be before this sends.) Thanks, that was exactly my point. Since el is at least 2, the average number of comparisons is no larger than 2, for any value of N. That's why, when I'm visually comparing MD5 values, I usually only look at the first few, and last few hex digits. However, Chris Angelico (at 10:39) pointed out again that totally random strings aren't real-world equivalent. He has now proposed that somebody measure real-world cases here, by patching the string comparison to gather statistics. I think that's beyond me at this point. I only joined this thread when the cases under study were well-defined random, and therefore predictable. <g> -- DaveA
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Comparing strings from the back? Roy Smith <roy@panix.com> - 2012-09-03 21:54 -0400
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-04 12:07 +1000
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-04 02:17 +0000
Re: Comparing strings from the back? Dan Sommers <dan@tombstonezero.net> - 2012-09-03 21:56 -0700
Re: Comparing strings from the back? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-04 08:50 +0100
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-04 18:32 +0200
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-04 18:07 +0000
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-05 11:17 +0200
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-05 07:59 +1000
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-05 11:24 +0200
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-05 11:43 +0200
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-05 14:30 +0000
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-05 16:51 +0200
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-05 16:24 +0000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-05 22:47 +0000
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-06 08:33 +0000
Re: Comparing strings from the back? Dave Angel <d@davea.name> - 2012-09-06 06:07 -0400
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-07 04:06 +0000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-07 19:10 +0000
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-08 00:55 +0000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-08 11:53 +0000
RE: Comparing strings from the back? "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-09-13 18:39 +0000
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-13 15:37 -0400
Re: Comparing strings from the back? alex23 <wuwei23@gmail.com> - 2012-09-13 20:48 -0700
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-14 00:46 -0400
Re: Comparing strings from the back? alex23 <wuwei23@gmail.com> - 2012-09-13 21:54 -0700
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-14 01:38 -0400
Re: Comparing strings from the back? alex23 <wuwei23@gmail.com> - 2012-09-13 23:06 -0700
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-14 04:03 -0400
Re: Comparing strings from the back? alex23 <wuwei23@gmail.com> - 2012-09-14 01:20 -0700
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-14 04:53 -0400
Re: Comparing strings from the back? alex23 <wuwei23@gmail.com> - 2012-09-14 03:26 -0700
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-14 07:36 -0400
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-14 10:16 +0000
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-14 07:43 -0400
RE: Comparing strings from the back? "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-09-14 22:43 +0000
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-14 23:10 -0400
Re: Comparing strings from the back? alex23 <wuwei23@gmail.com> - 2012-09-16 18:11 -0700
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-17 14:05 +1000
Re: Comparing strings from the back? alex23 <wuwei23@gmail.com> - 2012-09-16 23:06 -0700
Re: Comparing strings from the back? Ethan Furman <ethan@stoneleaf.us> - 2012-09-17 13:35 -0700
Re: Comparing strings from the back? Neil Hodgson <nhodgson@iinet.net.au> - 2012-09-18 09:14 +1000
Re: Comparing strings from the back? Ethan Furman <ethan@stoneleaf.us> - 2012-09-18 08:12 -0700
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-18 11:55 -0400
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-18 11:59 -0400
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-18 12:17 -0400
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-19 00:47 +0000
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-19 02:20 +1000
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-18 16:40 -0400
Re: Comparing strings from the back? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-19 00:48 +0100
Re: Comparing strings from the back? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-13 20:53 +0100
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-13 17:06 -0400
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-14 03:39 +0000
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-14 14:15 +1000
Re: Comparing strings from the back? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-13 22:17 +0100
Re: Comparing strings from the back? Dwight Hutto <dwightdhutto@gmail.com> - 2012-09-13 17:35 -0400
RE: Comparing strings from the back? "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-09-14 21:32 +0000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-07 19:40 +0000
Re: Comparing strings from the back? Gelonida N <gelonida@gmail.com> - 2012-09-08 17:52 +0200
Re: Comparing strings from the back? Duncan Booth <duncan.booth@invalid.invalid> - 2012-09-10 08:59 +0000
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-10 13:45 +0000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-10 14:06 +0000
Re: Comparing strings from the back? Duncan Booth <duncan.booth@invalid.invalid> - 2012-09-11 09:51 +0000
Re: Comparing strings from the back? Terry Reedy <tjreedy@udel.edu> - 2012-09-11 11:55 -0400
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-11 00:26 +1000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-10 14:32 +0000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-10 14:43 +0000
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-11 00:56 +1000
Re: Comparing strings from the back? Duncan Booth <duncan.booth@invalid.invalid> - 2012-09-11 09:41 +0000
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-06 12:04 +0100
Re: Comparing strings from the back? Steve Howell <showell30@yahoo.com> - 2012-09-14 17:51 -0700
Re: Comparing strings from the back? Roy Smith <roy@panix.com> - 2012-09-06 08:13 -0400
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-06 22:29 +1000
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-06 15:43 +0200
Re: Comparing strings from the back? Dave Angel <d@davea.name> - 2012-09-06 10:23 -0400
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-06 16:33 +0200
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-06 16:42 +0200
Re: Comparing strings from the back? Dave Angel <d@davea.name> - 2012-09-06 11:54 -0400
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-06 16:34 +0200
Re: Comparing strings from the back? Gelonida N <gelonida@gmail.com> - 2012-09-08 17:50 +0200
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-06 15:37 +0200
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-07 00:39 +1000
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-06 17:36 +0200
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-06 17:44 +0200
Re: Comparing strings from the back? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-07 04:07 +0000
Re: Comparing strings from the back? Terry Reedy <tjreedy@udel.edu> - 2012-09-04 01:13 -0400
Re: Comparing strings from the back? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-04 08:56 +0100
Re: Comparing strings from the back? Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2012-09-04 11:58 +0200
Re: Comparing strings from the back? Neil Hodgson <nhodgson@iinet.net.au> - 2012-09-05 12:18 +1000
Re: Comparing strings from the back? MRAB <python@mrabarnett.plus.com> - 2012-09-05 03:39 +0100
Re: Comparing strings from the back? Roy Smith <roy@panix.com> - 2012-09-04 22:48 -0400
Re: Comparing strings from the back? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-09-05 16:33 +0200
Re: Comparing strings from the back? Peter Otten <__peter__@web.de> - 2012-09-05 10:29 +0200
Re: Comparing strings from the back? Chris Angelico <rosuav@gmail.com> - 2012-09-05 18:33 +1000
Re: Comparing strings from the back? Peter Otten <__peter__@web.de> - 2012-09-05 11:48 +0200
Re: Comparing strings from the back? Peter Otten <__peter__@web.de> - 2012-09-05 17:45 +0200
Re: Comparing strings from the back? Dan Goodman <dg.gmane@thesamovar.net> - 2012-09-10 18:07 +0200
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-10 16:33 +0000
Re: Comparing strings from the back? Dan Goodman <dg.gmane@thesamovar.net> - 2012-09-10 19:32 +0200
Re: Comparing strings from the back? Dan Goodman <dg.gmane@thesamovar.net> - 2012-09-10 19:44 +0200
Re: Comparing strings from the back? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-09-10 21:52 +0000
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