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Re: puzzle with string permutations [photo]
From: |
Emanuel Berg |
Subject: |
Re: puzzle with string permutations [photo] |
Date: |
Wed, 08 Jun 2022 00:04:16 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) |
Yuri Khan wrote:
> This extension of the concept of sets is called a multiset
> or a bag. For each element, we also have a multiplicity.
> Let’s write it as {o:2, g:1, d:1}.
OK, cool!
> n_perm = (n_1 + ... + n_k)! / (n_1)! ... (n_k)!
Right, that's tedious to do programming of tho (but possible
of course) because of the expanding summation and
product ...
> This problem was part of my exam in maths when I was
> applying at Novosibirsk State University, Mechanics & Maths
> Department, in 1997.
:)
> You might also notice the formula is similar to that of
> a binomial coefficient: C_{n,k} = n! / k! (n-k)!. That's
> no coincidence.
That OTOH is easy to implement, but what is n and k exactly? Can you
use that here?
(defun binom (n k)
(/ (cl-faculty n)
(* (cl-faculty k)
(cl-faculty (- n k)) )))
--
underground experts united
https://dataswamp.org/~incal
- puzzle with string permutations [photo], Emanuel Berg, 2022/06/07
- Re: puzzle with string permutations [photo], Marcin Borkowski, 2022/06/07
- Re: puzzle with string permutations [photo], Emanuel Berg, 2022/06/07
- Re: puzzle with string permutations [photo], Emanuel Berg, 2022/06/07
- Re: puzzle with string permutations [photo], Emanuel Berg, 2022/06/07
- Re: puzzle with string permutations [photo], Emanuel Berg, 2022/06/07
- Re: puzzle with string permutations [photo], Emanuel Berg, 2022/06/07
- Re: puzzle with string permutations [photo], Yuri Khan, 2022/06/07
- Re: puzzle with string permutations [photo],
Emanuel Berg <=
- Re: puzzle with string permutations [photo], Emanuel Berg, 2022/06/07
- missing Lisp world (was: Re: puzzle with string permutations [photo]), Emanuel Berg, 2022/06/07
Re: puzzle with string permutations [photo], Emanuel Berg, 2022/06/07