A puzzle for Pythonistas

[Levente Sandor]

sandorlevi at yahoo.com (Levente Sandor) wrote in message news:<8b5e42a6.0302011309.2767717c at posting.google.com>...
> Pythonic? Elegant? Hmm...
Or stupid (like me), if you are'nt patient enough... :)

L1 = [1, 2, 3, 4, 5]
L2 = []
def combine(lst):
    if len(lst) > 1 and lst not in L2:
        L2.append(lst)
        for i in range(len(lst)):
            combine(lst[:i]+lst[i+1:])
combine(L1)
L2.sort()
L2.sort(lambda a, b: len(a)>len(b) and 1 or len(a)<len(b) and -1 or 0)
print L2    

----
levi


> 
> L1 = [1, 2, 3, 4, 5]
> L2 = []
> for i in range(len(L1)+1):
>     for j in range(i-1):
>         L2.append(L1[j:i])
> L2.sort(lambda a, b: len(a)>len(b) and 1 or len(a)<len(b) and -1 or 0)
> print L2
> 
> ----
> levi
> 
> alan_salmoni at yahoo.com (Alan James Salmoni) wrote in message news:<b68f71a7.0301310459.31539d3c at posting.google.com>...
> > Hi folks,
> > 
> > This is just a little puzzle to test your brains on - well, I should
> > come clean really, so what I need to do is work out a way to get all
> > the interactions from 2 or more variables for SalStat a small
> > statistics package, but to be honest, I am rather stuck on this bit.
> > 
> > The problem is defined like this: I have a list of unique integers,
> > and the list is of arbitrary length, though 2 elements is the minimum.
> > Using each integer only once, what are the possible combinations of 2
> > or more elements that can be derived from this list. I know how to
> > work out how many combinations there are: ((2**len(list))-1-len(list))
> > which is quite simple.
> > 
> > To illustrate:
> > 
> > If list = [1,2,3], then there are 4 possible combination: 1-2, 1-3,
> > 2-3, and 1-2-3.
> > If list = [1,2,3,4] then there are 11 possible combinations: 1-2, 1-3,
> > 1-4, 2-3, 2-4, 3-4, 1-2-3, 1-2-4, 1-3-4, 2-3-4, and 1-2-3-4.
> > 
> > All my ideas so far rely on brute force, and I was wondering if anyone
> > could think of an elegant and pythonic way of achieving the required
> > result.
> > 
> > I have a nasty feeling that the code may be complex, so feel free to
> > tell me to s0d off if you want! :)
> > 
> > Alan James Salmoni
> > SalStat Statistics
> > http://salstat.sunsite.dk