Re: Listing the partitions of a set
- To: mathgroup at smc.vnet.net
- Subject: [mg65302] Re: [mg65282] Listing the partitions of a set
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sat, 25 Mar 2006 05:17:37 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
Needs["DiscreteMath`Combinatorica`"]; s=SetPartitions[4] {{{1, 2, 3, 4}}, {{1}, {2, 3, 4}}, {{1, 2}, {3, 4}}, {{1, 3, 4}, {2}}, {{1, 2, 3}, {4}}, {{1, 4}, {2, 3}}, {{1, 2, 4}, {3}}, {{1, 3}, {2, 4}}, {{1}, {2}, {3, 4}}, {{1}, {2, 3}, {4}}, {{1}, {2, 4}, {3}}, {{1, 2}, {3}, {4}}, {{1, 3}, {2}, {4}}, {{1, 4}, {2}, {3}}, {{1}, {2}, {3}, {4}}} s/.{x_?NumberQ}:>x {{{1, 2, 3, 4}}, {1, {2, 3, 4}}, {{1, 2}, {3, 4}}, {{1, 3, 4}, 2}, {{1, 2, 3}, 4}, {{1, 4}, {2, 3}}, {{1, 2, 4}, 3}, {{1, 3}, {2, 4}}, {1, 2, {3, 4}}, {1, {2, 3}, 4}, {1, {2, 4}, 3}, {{1, 2}, 3, 4}, {{1, 3}, 2, 4}, {{1, 4}, 2, 3}, {1, 2, 3, 4}} Bob Hanlon > > From: Richard Palmer <mapsinc at bellatlantic.net> To: mathgroup at smc.vnet.net > Subject: [mg65302] [mg65282] Listing the partitions of a set > > > Is there a simple way to list the partitions of a set? For example, there > are 15 partitions on a set of 4 elements. {{{1, 2, 3, 4}}, {1, {2, 3, 4}}, > {{1, 3, 4}, 2}, {{1, 2, 4}, 3}, {{1, 2, 3}, 4}, {{1, 2}, {3, 4}}, {{1, > 3}, {2, 4}}, {{1, 4}, {2, 3}}, {1, 2, {3, 4}}, {1, 3, {2, 4}}, {1, 4, {2, > 3}}, {2, 3, {1, 4}}, {2, 4, {1, 3}}, {3, 4, {1, 2}}, {1, 2, 3, 4}} . > > >