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| Date | Fri, 10 Apr 2015 21:16:57 -0400 |
| From | Dave Angel <d@davea.name> |
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| Subject | Re: find all multiplicands and multipliers for a number |
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On 04/10/2015 09:06 PM, Dave Angel wrote: > On 04/10/2015 07:37 PM, ravas wrote: >> def m_and_m(dividend): >> rlist = [] >> dm = divmod >> end = (dividend // 2) + 1 >> for divisor in range(1, end): >> q, r = dm(dividend, divisor) >> if r is 0: >> rlist.append((divisor, q)) >> return rlist >> >> print(m_and_m(999)) >> --- >> output: [(1, 999), (3, 333), (9, 111), (27, 37), (37, 27), (111, 9), >> (333, 3)] >> --- >> >> How do we describe this function? >> Does it have an established name? >> What would you call it? >> Does 'Rosetta Code' have it or something that uses it? >> Can it be written to be more efficient? >> What is the most efficient way to exclude the superfluous inverse tuples? >> Can it be written for decimal numbers as input and/or output? >> >> Thank you! >> > > I'd call those factors of the original number. For completeness, I'd > include (999,1) at the end. > > If it were my problem, I'd be looking for only prime factors. Then if > someone wanted all the factors, they could derive them from the primes, > by multiplying all possible combinations. > > The program can be sped up most obviously by stopping as soon as you get > a tuple where divisor > q. At that point, you can just repeat all the > items, reversing divisor and q for each item. Of course, now I notice > you want to eliminate them. So just break out of the loop when divisor > > q. > > You can gain some more speed by calculating the square root of the > dividend, and stopping when you get there. > > But the real place to get improvement is to only divide by primes, > rather than every possible integer. And once you've done the division, > let q be the next value for dividend. So you'll get a list like > > [3, 3, 3, 37] > > for the value 999 > > See: > http://rosettacode.org/wiki/Factors_of_an_integer#Python > > And http://rosettacode.org/wiki/Prime_decomposition#Python There the function that you should grok is decompose() -- DaveA
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find all multiplicands and multipliers for a number ravas <ravas@outlook.com> - 2015-04-10 16:37 -0700
Re: find all multiplicands and multipliers for a number Dave Angel <d@davea.name> - 2015-04-10 21:16 -0400
Re: find all multiplicands and multipliers for a number Dave Angel <davea@davea.name> - 2015-04-10 21:06 -0400
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-11 12:04 +1000
Re: find all multiplicands and multipliers for a number Stephen Tucker <stephen_tucker@sil.org> - 2015-04-11 06:11 +0100
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-10 23:08 -0700
Re: find all multiplicands and multipliers for a number Marko Rauhamaa <marko@pacujo.net> - 2015-04-11 10:14 +0300
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-11 09:59 -0700
Re: find all multiplicands and multipliers for a number Marko Rauhamaa <marko@pacujo.net> - 2015-04-11 20:31 +0300
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-11 10:52 -0700
Re: find all multiplicands and multipliers for a number Chris Angelico <rosuav@gmail.com> - 2015-04-12 07:10 +1000
Re: find all multiplicands and multipliers for a number Terry Reedy <tjreedy@udel.edu> - 2015-04-11 19:58 -0400
Re: find all multiplicands and multipliers for a number Chris Angelico <rosuav@gmail.com> - 2015-04-12 10:16 +1000
Re: find all multiplicands and multipliers for a number wolfram.hinderer@googlemail.com - 2015-04-11 16:17 -0700
Re: find all multiplicands and multipliers for a number Marko Rauhamaa <marko@pacujo.net> - 2015-04-12 10:17 +0300
Primes [was Re: find all multiplicands and multipliers for a number] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-12 20:48 +1000
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-12 18:56 -0700
Re: find all multiplicands and multipliers for a number Dave Angel <davea@davea.name> - 2015-04-12 22:35 -0400
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-12 20:30 -0700
Re: find all multiplicands and multipliers for a number Dave Angel <davea@davea.name> - 2015-04-13 00:35 -0400
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-12 22:25 -0700
Re: find all multiplicands and multipliers for a number Dave Angel <davea@davea.name> - 2015-04-13 01:43 -0400
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-12 22:57 -0700
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-13 17:21 +1000
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-13 19:42 -0700
Re: find all multiplicands and multipliers for a number Chris Angelico <rosuav@gmail.com> - 2015-04-14 12:47 +1000
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-13 19:54 -0700
Re: find all multiplicands and multipliers for a number Rustom Mody <rustompmody@gmail.com> - 2015-04-14 03:35 -0700
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-14 23:30 +1000
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-14 23:40 +1000
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-14 19:37 -0700
Re: find all multiplicands and multipliers for a number Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-15 09:59 -0600
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-15 09:21 -0700
Re: find all multiplicands and multipliers for a number Chris Kaynor <ckaynor@zindagigames.com> - 2015-04-15 09:46 -0700
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-15 10:37 -0700
Searching the archives Gil Dawson <Gil@GilDawson.com> - 2015-04-15 11:47 -0700
Installing Python Gil Dawson <Gil@GilDawson.com> - 2015-04-15 12:09 -0700
Re: Searching the archives Tim Golden <mail@timgolden.me.uk> - 2015-04-15 20:16 +0100
Re: Installing Python Ned Deily <nad@acm.org> - 2015-04-15 13:32 -0700
Re: find all multiplicands and multipliers for a number Rustom Mody <rustompmody@gmail.com> - 2015-04-15 21:17 -0700
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-11 17:35 +1000
Re: find all multiplicands and multipliers for a number jonas.thornvall@gmail.com - 2015-04-11 01:47 -0700
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-11 09:31 -0700
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-12 12:22 +1000
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-11 21:24 -0700
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-12 14:29 +1000
Re: find all multiplicands and multipliers for a number Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-04-11 12:41 -0400
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-11 10:02 -0700
Re: find all multiplicands and multipliers for a number Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-04-11 12:37 -0400
Re: find all multiplicands and multipliers for a number Brian Gladman <blindanagram@nowhere.net> - 2015-04-12 10:34 +0100
Re: find all multiplicands and multipliers for a number Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-13 00:29 +1000
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-12 10:20 -0700
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-12 10:23 -0700
Re: find all multiplicands and multipliers for a number Brian Gladman <blindanagram@nowhere.net> - 2015-04-12 20:15 +0100
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-12 12:45 -0700
Re: find all multiplicands and multipliers for a number Brian Gladman <blindanagram@nowhere.net> - 2015-04-12 20:07 +0100
Re: find all multiplicands and multipliers for a number Paul Rubin <no.email@nospam.invalid> - 2015-04-10 18:28 -0700
Re: find all multiplicands and multipliers for a number Dave Farrance <DaveFarrance@OMiTTHiSyahooANDTHiS.co.uk> - 2015-04-11 10:03 +0100
Re: find all multiplicands and multipliers for a number ravas <ravas@outlook.com> - 2015-04-11 10:11 -0700
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