Re: Binary System Problem
- To: mathgroup at smc.vnet.net
- Subject: [mg18679] Re: [mg18621] Binary System Problem
- From: Robert Pratt <rpratt at math.unc.edu>
- Date: Thu, 15 Jul 1999 01:45:59 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Needs["DiscreteMath`Combinatorica`"]
toBinary[lis_List,n_]:=Table[If[MemberQ[lis,i],1,0],{i,1,n}]
frieder[n_,k_]:=Map[toBinary[#,n]&,KSubsets[Range[n],k]]
frieder[5,4]
{{1,1,1,1,0},{1,1,1,0,1},{1,1,0,1,1},{1,0,1,1,1},{0,1,1,1,1}}
You can go back and forth between the lists of binary digits and the
decimal numbers as follows.
Map[FromDigits[#,2]&,frieder[5,4]]
{30,29,27,23,15}
Map[IntegerDigits[#,2]&,%]
{{1,1,1,1,0},{1,1,1,0,1},{1,1,0,1,1},{1,0,1,1,1},{1,1,1,1}}
Rob Pratt
Department of Mathematics
The University of North Carolina at Chapel Hill
CB# 3250, 331 Phillips Hall
Chapel Hill, NC 27599-3250
rpratt at math.unc.edu
http://www.math.unc.edu/Grads/rpratt/
On Tue, 13 Jul 1999, Frieder Schweigert wrote:
> Hi,
>
> does anybody know an algorithm or generating system for
> those binary numbers with a fix amount of '1's,
> for example (four times '1'):
>
> 1111
> 10111
> 11011
> 11101
> 11110
>