Re: permutations

*To*: mathgroup at smc.vnet.net*Subject*: [mg62421] Re: permutations*From*: "Scout" <Scout at nodomain.com>*Date*: Thu, 24 Nov 2005 06:33:20 -0500 (EST)*References*: <dm1jov$n4c$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

"Francisco Gutierrez" <fgutiers2002 at yahoo.com> > Dear Group: > If I do for example: > Permutations[{x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x11,x12}], > my computer runs out of memory. > This is not such a poor computer. Actually, I would need to do > permutations of lists of Length 20, perhaps 25. I am aware these > calculations are big (Length[x]!), but I wonder if there is some way > around the problem. Compilating Permutations? But then how? Can somebody > help me? > Francisco Gutiérrez > > > Hi Francisco, have you already tried to use the NextPermutation[] function? Let's say l={x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x11,x12} NextPermutations[ l ] gives {x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x12,x11} that differ from the previous list in only one change. So, applying repeatedly NextPermutation[] you can cover all the Length[l]! permutations. I hope this help you, ~Scout~