On Tue, May 15, 2012 at 08:33:23AM -0700, tvn wrote:
> I am wondering if Sage has some functions to generate the below
> given N,K (both are non-neg ints), return a set of tuples (n1...nk)
> such that ni >= 0 and sum(ni)= N.
>
> So if N=5,k=2, then there are 6 tuples (5,0) (4,1) ... (0,5) .
>
> Is there a name for this problem ?
sage: C = IntegerVectors(5,2)
sage: C.list()
[[5, 0], [4, 1], [3, 2], [2, 3], [1, 4], [0, 5]]
sage: C.cardinality()
6
> what is the # of tuples for the given N,K ?
Use introspection to find the class of C:
sage: C??
and look up the cardinality method. Then prove the formula :-)
Kind regards,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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