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Re: how to get the longest ordered sub sequence of a list in

• To: mathgroup at smc.vnet.net
• Subject: [mg103177] Re: how to get the longest ordered sub sequence of a list in
• From: Emu <samuel.thomas.blake at gmail.com>
• Date: Thu, 10 Sep 2009 07:17:34 -0400 (EDT)
• References: <h87pgp$5gt$1@smc.vnet.net>

On Sep 9, 6:37 pm, a boy <a.dozy.... at gmail.com> wrote:
> how to get a (strict or not-strict)decreasing sub sequence of a list?
>                                     =
         ----------------
>
> increasing                               =
    ?

Try using Split.

In[185]:= lst=RandomInteger[{1,5},20]
Out[185]= {4,3,4,2,4,1,3,5,3,2,3,4,3,4,2,5,5,5,5,5}

In[186]:= Split[lst, #1 >= #2 &]
Out[186]= {{4, 3}, {4, 2}, {4, 1}, {3}, {5, 3, 2}, {3}, {4, 3}, {4,
2}, {5, 5, 5, 5, 5}}

Then you can find the longest non-strictly decreasing sub sequence as
follows.

In[187]:= m = Max[Length /@ %];
Select[%%, Length[#] == m &]

Out[188]= {{5, 5, 5, 5, 5}}

Sam

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  • Re: Re: how to get the longest ordered sub sequence of a
    • From: DrMajorBob <btreat1@austin.rr.com>