From: Christoph Bauer <c_bauer@informatik.uni-kl.de>
To: OCaml List <caml-list@inria.fr>
Subject: Re: [Caml-list] Should be INSIDE STANDARD-LIB: Hashtbl.keys
Date: Fri, 23 Apr 2004 19:27:23 +0200 [thread overview]
Message-ID: <m3ekqeehac.fsf@diebuntekuh.de> (raw)
In-Reply-To: <Pine.LNX.4.44.0404231054160.9460-100000@localhost.localdomain> (Brian Hurt's message of "Fri, 23 Apr 2004 11:06:06 -0500 (CDT)")
Brian Hurt <bhurt@spnz.org> writes:
> let uniq lst =
> let rec loop accum = function
> | [] -> List.rev accum
> | x :: [] -> List.rev (x :: accum)
> | x :: y :: t ->
> if (x = y) then
> loop accum (x :: t)
> else
> loop (x :: accum) (y :: t)
> in
> loop [] lst
> ;;
I found these lines in my code:
let unique list =
let h = Hashtbl.create (2*List.length list) in
List.filter
(fun a ->
let known = Hashtbl.mem h a in
Hashtbl.add h a true;
not known) list
On average Hashtbl.mem should take 2 accesses. So this algorithm
runs in O(n). (But the worst case is very bad.)
Regards,
Christoph Bauer
--
beginfig(1)u=3cm;draw fullcircle scaled 2u;x0=x1=y1=x2=y3=0;-y0=y2=x3=1u;
filldraw z0..{left}z1{left}..z2{curl 1}..z3..z0..cycle;def t(expr p)=fullcircle
scaled .25u shifted(0,p*u);enddef;unfill t(.5);fill t(-.5);endfig;bye
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next prev parent reply other threads:[~2004-04-23 17:24 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-04-21 1:19 Oliver Bandel
2004-04-21 8:39 ` Richard Jones
2004-04-21 9:13 ` Martin Jambon
2004-04-23 12:51 ` Xavier Leroy
2004-04-23 13:05 ` Jean-Baptiste Rouquier
2004-04-23 16:04 ` Xavier Leroy
2004-04-23 18:21 ` Jon Harrop
2004-04-23 21:31 ` Jon Harrop
2004-04-23 21:53 ` John Goerzen
2004-04-26 6:28 ` Florian Hars
2004-04-23 18:29 ` John Goerzen
[not found] ` <20040423190710.GA1506@first.in-berlin.de>
2004-04-23 20:42 ` John Goerzen
2004-04-23 15:03 ` Richard Jones
2004-04-24 1:58 ` skaller
2004-04-24 9:20 ` Nicolas Cannasse
2004-04-24 19:26 ` skaller
2004-04-26 7:29 ` Jean-Christophe Filliatre
2004-04-23 16:06 ` Brian Hurt
2004-04-23 16:31 ` Martin Jambon
2004-04-23 17:27 ` Christoph Bauer [this message]
2004-04-23 18:29 ` John Goerzen
[not found] ` <20040423191010.GB1506@first.in-berlin.de>
2004-04-23 20:41 ` John Goerzen
[not found] ` <20040424080904.GA821@first.in-berlin.de>
2004-04-24 20:59 ` John Goerzen
2004-04-25 8:12 ` Oliver Bandel
2004-04-23 18:28 ` John Goerzen
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