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MathGroup Archive 2004

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Re: Challenge: Fastest method to convert positive integers to 1 in a long list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52186] Re: [mg52172] Challenge: Fastest method to convert positive integers to 1 in a long list
  • From: Selwyn Hollis <sh2.7183 at misspelled.erthlink.net>
  • Date: Sun, 14 Nov 2004 04:30:28 -0500 (EST)
  • References: <200411130940.EAA01037@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On Nov 13, 2004, at 4:40 AM, Carl K. Woll wrote:

> Hi all,
>
> Inspired by the recent thread on counting runs, I have the following
> challenge. Come up with a method to convert all the positive integers 
> in a
> long sequence of nonnegative integers to 1, so that the sequence 
> consists of
> only 0s and 1s. Let the sequence be given by
>
> seq = Table[Random[Integer, 10], {10^6}];
>
> Then, one technique is
>
> newseq = 1+Quotient[#,#+1,1]&@seq;
>
> Can anyone do better?
>
> Carl Woll


This one seems a tad faster:

(newseq = Mod[#+2,#+1]&@seq;) // Timing

{0.16 Second, Null}

versus your

(newseq = 1 + Quotient[#,#+1,1]&@seq;) // Timing

{0.23 Second, Null}


-----
Selwyn Hollis
http://www.appliedsymbols.com
(edit reply-to to reply)


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