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MathGroup Archive 2007

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Re: Increasing scattered subsequence

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80116] Re: Increasing scattered subsequence
  • From: "Dana DeLouis" <dana.del at gmail.com>
  • Date: Mon, 13 Aug 2007 04:28:05 -0400 (EDT)

>>> Write a function maxima[lis_List] which, given a list of numbers,
>>> produces a list of those numbers greater than all those
>>> that precede them. For example
>>>
>>> maxima[{ 9, 2, 10, 3, 14, 9}] returns { 9, 10, 14}.

I'm missing some of the thread, but here's my attempt:

Maxima[v_?VectorQ] := UnsortedUnion[FoldList[Max[#1, #2] & , 
       First[v], Rest[v]]]

UnsortedUnion[x_] := Reap[Sow[1, x], _, #1 & ][[2]]


Maxima[{9, 2, 10, 3, 14, 9}]

{9, 10, 14}

Timing[Maxima[RandomPermutation[50]]]

{0., {12, 22, 39, 40, 46, 49, 50}}

-- 
HTH   :>)
Dana DeLouis

Mathematica 6.0
Having to use Mathematica 5.2 Help files
Studying Mathematica 4.0 Book




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