MathGroup Archive 2006

[Date Index] [Thread Index] [Author Index]

Search the Archive

subsets of a set


In page 226 of John Gray's Mastering Mathematica
(unfortunately I had the 1994's edition)
there is the following exercise:

"Given a finite set (presented as a list) and an integer k
find all k-element subsets of the set".

There is one solution however for practicing (no there is no professor
that asked me this for homeworks! I work individually...) I search for
other

So considering the following list

lst = Tuples[Range[7], 3];

I can erase the sublists containg at least two same elements

Cases[lst, {x_, y_, z_} /; x ß?  y && x ß?  z && y ß?  z]

but after I cannot erase the permutations of e.g. {1,2,3};
that is in the output there are the sublists {1,2,3},
{2,1,3},{3,1,2} e.t.c. for other triplets.

I look for both functional as well pattern matching approaches.

Thanks


  • Prev by Date: Re: Vector operations,
  • Next by Date: Re: [RESEND] How to tell Mathematica to use hardware floating point aithmetics
  • Previous by thread: tableform question
  • Next by thread: subsets of a set