Tom Jones wrote:
> Hi,
>
> Consider tuples of the above numbers in the form:
> (a,b)
>
> Suppose this relation means:
> a depends on b
>
> Given a list of tuples, I would like an algorithm to return the proper
> ordering of the elements...and if the ordering has a loop (which in this
> case, prevents a proper ordering), then it should return None.
>
You want what's called a topological sort, see:
http://blog.vrplumber.com/scripts/toposort.py
for a pair of old algorithms from Tim Peters and I. I believe we raise
errors on loops, but that's pretty trivial to change.
Have fun,
Mike
--
________________________________________________
Mike C. Fletcher
Designer, VR Plumber, Coder
http://www.vrplumber.com
http://blog.vrplumber.com
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