Re: bit count or bit set && Python3

From	Neil Cerutti <neilc@norwich.edu>
Newsgroups	comp.lang.python
Subject	Re: bit count or bit set && Python3
Date	2012-10-26 12:56 +0000
Organization	Norwich University
Message-ID	<aevfjqFaa5tU3@mid.individual.net> (permalink)
References	(1 earlier) <k6bllq$3gt$1@ger.gmane.org> <mailman.2849.1351179123.27098.python-list@python.org> <50896152$0$29978$c3e8da3$5496439d@news.astraweb.com> <aetk2pFsd2rU3@mid.individual.net> <mailman.2864.1351196432.27098.python-list@python.org>

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On 2012-10-25, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Thu, Oct 25, 2012 at 2:00 PM, Neil Cerutti
> <neilc@norwich.edu> wrote:
>> Yes indeed! Python string operations are fast enough and its
>> arithmetic slow enough that I no longer assume I can beat a
>> neat lexicographical solution. Try defeating the following
>> with arithmetic:
>>
>> def is_palindrom(n):
>>    s = str(n)
>>    return s = s[::-1]
>
> Problems like these are fundamentally string problems, not math
> problems.  The question being asked isn't about some essential
> property of the number,  but about its digital representation.
> Certainly they can be reasoned about mathematically, but the
> fact remains that the math being done is about the properties
> of strings.

The "unexpected" part, to me, is that an optimal arithmetic based
solution conceptually is more efficient. You need to compute just
half the digits of the number and then perform a contant compare
operation.

-- 
Neil Cerutti

Thread

Re: bit count or bit set && Python3 Chris Angelico <rosuav@gmail.com> - 2012-10-26 02:31 +1100
  Re: bit count or bit set && Python3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-25 15:57 +0000
    Re: bit count or bit set && Python3 rusi <rustompmody@gmail.com> - 2012-10-25 09:17 -0700
      Re: bit count or bit set && Python3 Chris Angelico <rosuav@gmail.com> - 2012-10-26 03:29 +1100
        Re: bit count or bit set && Python3 rusi <rustompmody@gmail.com> - 2012-10-25 09:37 -0700
      Re: bit count or bit set && Python3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-10-25 17:44 +0100
      Re: bit count or bit set && Python3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-25 17:16 +0000
    Re: bit count or bit set && Python3 Serhiy Storchaka <storchaka@gmail.com> - 2012-10-25 22:07 +0300
    Re: bit count or bit set && Python3 Neil Cerutti <neilc@norwich.edu> - 2012-10-25 20:00 +0000
      Re: bit count or bit set && Python3 Neil Cerutti <neilc@norwich.edu> - 2012-10-25 20:04 +0000
      Re: bit count or bit set && Python3 Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-25 14:20 -0600
        Re: bit count or bit set && Python3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-25 23:48 +0000
        Re: bit count or bit set && Python3 Neil Cerutti <neilc@norwich.edu> - 2012-10-26 12:56 +0000
    Re: bit count or bit set && Python3 Charles Hixson <charleshixsn@earthlink.net> - 2012-10-25 09:08 -0700
    Re: bit count or bit set && Python3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-10-25 22:51 +0100

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