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. For example, [(1,2),(2,3),(3,4)] should give: [4,3,2,1] [(3,2),(1,3),(2,4)] should give: [4,2,3,1] [(1,4),(4,3),(2,3)] should give: [3,2,4,1] or [3,4,2,1] (which one doesn't matter) [(1,2), (2,3), (3,2)] should give None, since it cannot be resolved I'm sure this is a standard problem (mro, resolving inheritance?), but this is a simplified case since each element can directly depend on only one other element (thus, multiple inheritance is not allowed)...but many elements can depend on the same element (no limit on the number of classes which subclass another class). A quick hack is simple enough to code, but I am wondering if there are 'standard' ways of performing this task in this limited scope. Thanks. -- http://mail.python.org/mailman/listinfo/python-list
