[Chicago] Problems with Merge Sort???

Mon Jun 15 14:10:08 CEST 2015

Hi Douglas, I just worked through this problem myself over the weekend. are
you doing this course by chance?
http://interactivepython.org/runestone/static/pythonds/index.html

Anyway, could you share a link to your code? Hard to make suggestions
without seeing it.

-Aziz
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Today's Topics:

   1. Re: Question about using Sympy. (Joshua Herman)
   2. Problems with Merge Sort??? (Lewit, Douglas)
   3. Not exactly a solution, but.... (Lewit, Douglas)

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Message: 1
Date: Sun, 14 Jun 2015 19:38:03 -0500
From: Joshua Herman <zitterbewegung at gmail.com>
To: The Chicago Python Users Group <chicago at python.org>
Subject: Re: [Chicago] Question about using Sympy.
Message-ID:
        <CAB3V1zmkq_Lj_nitb1PkZk+m6PtrH0Dq824zBVPBgWf7NbszxQ at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

>From the documentation
http://docs.sympy.org/dev/modules/solvers/solvers.html#module-sympy.solvers.recurr

On Thu, Jun 11, 2015 at 10:45 PM, Lewit, Douglas <d-lewit at neiu.edu> wrote:

> Hi there Chipy Folks,
>
> Just wondering if the sympy module has a builtin routine for solving
> recurrence relations.  If you know, please enlighten me.  I know that
Maple
> and Mathematica have such routines--and they are pretty impressive.  Just
> wondering if the sympy module has something equivalent.
>
> Thanks and I hope everyone in the group has a fun weekend.  I'm looking
> forward to Wednesday evening's meeting at Pumping Station One.  I'll be
> arriving right after my second Algorithms exam, so there's a chance I
won't
> be in a very happy mood!  That course is just brutal.  The prof got his
> undergrad degree at Harvard and his PhD. at the University of Chicago.  A
> real genius.... and also extremely demanding!  So wish me luck on that
> exam!   :-)
>
> Warm regards,
>
> Douglas.
>
> _______________________________________________
> Chicago mailing list
> Chicago at python.org
> https://mail.python.org/mailman/listinfo/chicago
>
>
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Message: 2
Date: Sun, 14 Jun 2015 23:31:24 -0500
From: "Lewit, Douglas" <d-lewit at neiu.edu>
To: The Chicago Python Users Group <chicago at python.org>
Subject: [Chicago] Problems with Merge Sort???
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Hey guys,

I'm trying to master the merge sort algorithm and definitely experiencing
some failure.  My merge program works great.  It takes two arrays, and
assuming that they are already sorted, the two sorted arrays get merged
together into one unified sorted array.  So that's not the problem.

The problem is my mergeSort program.  I inserted a couple of print
statements to print out the intermediate results of the recursion, and it
appears that all my program does is break the array down into pieces and
then rebuilds the pieces.... into the original array!  (Could be worse I
guess.  No error messages!  But the output is totally useless.)  I'm
honestly at a loss.  I know I'm really close to the right solution, but
there is something that I'm missing and I can't figure it out.  I've been
struggling with this for a couple days now, and I'm ready to give up.  Can
someone please enlighten me?

Thanks!!!

Best,

Douglas.
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Message: 3
Date: Mon, 15 Jun 2015 02:29:32 -0500
From: "Lewit, Douglas" <d-lewit at neiu.edu>
To: The Chicago Python Users Group <chicago at python.org>
Subject: [Chicago] Not exactly a solution, but....
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I sort of got my mergeSort program to work, but the problem is that the
algorithm isn't really mergeSort at all!  It uses merge, but my algorithm
is iterative rather than recursive, so it's not really a mergeSort.  It's a
merge-something, but not true mergeSort.  Oh well.  Any suggestions?
Thanks!

Best,

Douglas.
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