subsets of a set
- To: mathgroup at smc.vnet.net
- Subject: [mg70001] subsets of a set
- From: dimmechan at yahoo.com
- Date: Sat, 30 Sep 2006 05:12:23 -0400 (EDT)
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