Algorithm: combinations of (k) taken from (n) values

[Matthew Hirsch]

Thanks for your help.  This is exactly how I pictured it, starting with 
lists of numbers up to n, and then adding on to them from there.

Matt




In article <38ED5285.719F26D7 at udel.edu>, Charles Boncelet 
<boncelet at udel.edu> wrote:

> Matthew Hirsch wrote:
> 
> > Hi All,
> >
> > Onto the next question...
> >
> > Can anyone think of an algorithm to store as lists all possible
> > combinations of k numbers taken from n possible numbers.  For example,
> > given 5 values, I want to choose 2.  The number of possible combinations
> > is given by 5!/(3!2!)=10.  They are:
> >
> 
> Funny you should ask, since I just wrote one two days ago:
> 
> def combs(n,k=None):
>     """returns sorted list of k items taken from n."""
>     if k==None:
>         k=n
>     l = []
>     for c in range(n):
>         l.append([c])
>     for i in range(k-1):
>         li = []
>         for c in l:
>             for j in range(c[-1]+1,n):
>                 li.append(c+[j])
>         l = li
>     return l
> 
>     Charlie Boncelet
> ------
> Charles Boncelet, University of Delaware,
> On sabbatical at ADFA, Canberra Australia,
> Home Page: http://www.ece.udel.edu/~boncelet/
> 
>