Path: news.mathworks.com!not-for-mail From: "John D'Errico" <woodchips@rochester.rr.com> Newsgroups: comp.soft-sys.matlab Subject: Re: integer solutions for x_1+x_2+...+x_n = k Date: Tue, 4 Nov 2008 21:31:04 +0000 (UTC) Organization: John D'Errico (1-3LEW5R) Lines: 28 Message-ID: <geqeuo$m4e$1@fred.mathworks.com> References: <geku21$eku$1@fred.mathworks.com> <gel0b6$3li$1@fred.mathworks.com> <geqe85$chp$1@fred.mathworks.com> Reply-To: "John D'Errico" <woodchips@rochester.rr.com> NNTP-Posting-Host: webapp-02-blr.mathworks.com Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8bit X-Trace: fred.mathworks.com 1225834264 22670 172.30.248.37 (4 Nov 2008 21:31:04 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Tue, 4 Nov 2008 21:31:04 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 869215 Xref: news.mathworks.com comp.soft-sys.matlab:498955 "Oriole " <oriole_ni@hotmail.com> wrote in message <geqe85$chp$1@fred.mathworks.com>... > "Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <gel0b6$3li$1@fred.mathworks.com>... > > > > > Have you check the number of solutions for large n? It might be not possible to compute. > > > > Here is code in FEX that can accomplish that, but again, try to look at the feasibility before solving: http://www.mathworks.com/matlabcentral/fileexchange/17818 > > > > Bruno > > Hi, Bruno, > > Thank you for the help. Your subfunction v=allVL1eq(n, L1, head) works fine for my problem. But I have some difficulty in understanding the recursive algorithm. I know it does the job, and more or less how it works, but still feel confused about it. What is the basic idea of this recursive algorithm? would you like to explain a litle bit for me... Lots of thanks > > /Oriole You can look at my partitions function on the file exchange. It is certainly less elegant than Bruno's code as I recall, although it is still recursive. The idea behind these recursive methods to find the partitions of the number k is to pick a value for x1. Once you have done that, you are now looking for all the partitions of k-x1. Repeat recursively until done. John