Re: Finding Position in an ordered list
- To: mathgroup at smc.vnet.net
- Subject: [mg57737] Re: Finding Position in an ordered list
- From: dh <dh at metrohm.ch>
- Date: Tue, 7 Jun 2005 02:03:38 -0400 (EDT)
- References: <d811k4$cch$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi Janos,
I think "DiscreteMath`Combinatorica`BinarySearch" is what you are
searching for.
?BinarySearch
BinarySearch[l, k] searches sorted list l for key k and gives the
position of l containing k, if k is present in l. Otherwise, if k is
absent in l, the function returns (p + 1/2) where k falls between the
elements of l in positions p and p+1. BinarySearch[l, k, f] gives the
position of k in the list obtained from l by applying f to each element
in l.
sincerely, Daniel
janostothmeister at gmail.com wrote:
> I wonder if it is possible to use the knowledge
> that a list in which I am looking for the position
> of an element is ordered. I want a quicker solution then e.g.
> lis={ac,dmk,rfg,sty,zxxer}
> Position[lis,sty]
>
> I am certainly interested in longer lists...
>
> Thank you,
>
> Janos
>
>