RE: subsets of a set
- To: mathgroup at smc.vnet.net
- Subject: [mg70051] RE: [mg70001] subsets of a set
- From: "Erickson Paul-CPTP18" <Paul.Erickson at Motorola.com>
- Date: Sun, 1 Oct 2006 04:09:40 -0400 (EDT)
Do you want
lst = Subsets[Range[7], {3}]
?
-----Original Message-----
From: dimmechan at yahoo.com [mailto:dimmechan at yahoo.com]
To: mathgroup at smc.vnet.net
Subject: [mg70051] [mg70001] 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