dependency order

[belred at gmail.com]

i'm having trouble trying to figure this out... it's part of a build
system i'm writing in python.  maybe someone has a good simple way to
solve this.  i'm trying to create a dependency order out of multiple
lists.

list1: B C
list2: A B
list3: A C

i want the end result to be the list: A B C
i'm very frustrated that i can't come up with anything that always
works.


thanks... any clues to solve this would be greatly appreciated.

bryan