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Re: Filtering a list of list for certain elements that are neighbours

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88840] Re: [mg88834] Filtering a list of list for certain elements that are neighbours
  • From: Curtis Osterhoudt <cfo at lanl.gov>
  • Date: Mon, 19 May 2008 05:14:59 -0400 (EDT)
  • Organization: LANL
  • References: <200805181134.HAA23914@smc.vnet.net>
  • Reply-to: cfo at lanl.gov

  Here's another possibility, which might give more flexibility (not sure). I 
couldn't figure out how to combine the "or" statements inside one Cases 
argument -- any clues? 

   In[1011]:= Cases[Cases[mylist, Except[{___, a, b, ___}]], 
 Except[{___, b, a, ___}]]

Out[1011]= {{a, c, b}, {b, c, a}}

                     Cheers, 
                           C.O.

On Sunday 18 May 2008 05:34:18 Steven Siew wrote:
> I have a list of lists
>
> mylist={{a,b,c},{a,c,b},{b,a,c},{b,c,a},{c,a,b},{c,b,a}}
>
> I want to filter out all lists that have "a being a neighbor to b".
>
> I am looking for the following result.
>
> {{a,c,b},{b,c,a}}
>
>
> For this toy example, I can probably do it by hand but my real problem
> has 120 lists in a list. And I need to filter out various combination
> of letters like "s cannot be next to d" , "s cannot be next to j" , "c
> cannot be next to j" , "h cannot be next to d" and "h cannot be next
> to s".



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