in reply to RE: RE: Re: All array elements the same?
in thread All array elements the same?

...proving that brute force is not always a Bad Thing (tm), and that non-brute force methods can be a Bad Thing (tm), depending on your purpose and perspective.

IMHO: Given all the above descriptions, I would consider the hash method brute force and in this case, the more efficient method.

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RE: RE: RE: RE: Re: All array elements the same?
by lhoward (Vicar) on Aug 01, 2000 at 22:52 UTC
    I agree, except in your assertion that the hash brute-force method is best.

    Performance wise the hash method will always take O(n) time, even if the first and second elements of the lists are different. An appriach like what I present below can bail-out if it finds a mismatch before examining the entire list. Therefore giving it a better average and best-case performance for lists that don't have homogeneous contents. 

    sub is_list_homegeneous{
  my @list=@_;
  my $val=shift @list;
  foreach(@list){
    return 0 if($_ ne $val)
  }
  return 1;
}

    [download]
    This is not as short and cool, but does have better algorithmic performance. You could tweak-out the overhead I incurred by copying the list if you wanted the utmost in speed. My technique is probably slightly slower worse-case (a homogeneous list), because it does do slightly more work.
[reply]
[d/l]
      Should I start stripping RE:'s out of the subject line?

      Anyway, I sit corrected regarding speed. At worst case, your code is ever-so-slightly slower than 0(n).

      Thanks so much, for the discussion. It's proven to be a learning experience! -eLore

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