Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: A list of numbers without "73"

  • To: mathgroup at smc.vnet.net
  • Subject: [mg63020] Re: [mg63005] A list of numbers without "73"
  • From: gardyloo <gardyloo at mail.wsu.edu>
  • Date: Sun, 11 Dec 2005 04:56:42 -0500 (EST)
  • References: <200512101103.GAA29418@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Thomas Schmelzer wrote:

>Experts,
>
>S(i) should be a list of positive integers without the substring "73".
>
>My code seems to be very inefficient. I multiply all numbers with 0 if they 
>contain "73", sort the new list, make the union (remove double elements) and 
>delete the first element. Therefore it is necessary to use an if statement 
>in order not to delete the first element of the numbers 1-9. Any more 
>sophisticated ideas?
>
>L := Table[k, {k, 1, 9}]
>
>S[i_] := S[i] =
>If[i == 1, L,
>Delete[Union[
>Table[k*(1 - Boole[StringMatchQ[ToString[k], "*73*"]]), {k,
>10^(i - 1), 10^i - 1}]], 1]]
>
>
>
>Best
>
>Thomas
>

  Hi, Thomas,

       I don't know about the timing issues inherent with using Select
(does it check _each_ member of its enclosed list; might, perhaps, an if
statement for the power "i" used in Range be more efficient? I'm too
lazy to do rigorous checks), but this should work for you:

S[i_] := Select[Range[10^(i - 1), 10^i - 1], #1 != 73 & ]


In[32]:=
$Version

Out[32]=
5.2 for Linux (June 20, 2005)
 

       Best of luck,
               C.O.



  • Prev by Date: Re: A list of numbers without "73"
  • Next by Date: Simple task with Mathematica
  • Previous by thread: Re: A list of numbers without "73"
  • Next by thread: Re: A list of numbers without "73"