Java: Generate a Powerset
This could be language agnostic/helpful answers could just be in pseudo-code.
I have a program that I would like to test under a range of inputs. This program takes a set of files, one of which is designated as the root. I want to run the program with all possible subsets of files. (Two subsets, containing the same files, but with different roots, are considered to be different.)
Here's a same example. Say I have files A, B, and C. I would want to test with:
{A}, root = A
{B}, root = B
{C}, roo开发者_如何学运维t = C
{A B}, root = A
{A B}, root = B
{B C}, root = B
{B C}, root = C
{A C}, root = A
{A C}, root = C
{A B C}, root = A
{A B C}, root = B
{A B C}, root = C
and so on. I believe this would be the powerset.
What is the best way to generate this set in Java, given a directory full of files?
You said Java, but please take a look on this: Permutations, Combinations, and Variations using C# Generics.
Here's pseudocode for a recursive approach to doing tests on all possible mixes.largest-subsets-first:
allofthem = set(listallfiles(thedir))
function trythemall(someset):
if someset is empty: return
for entry in someset:
dotest(someset, root=entry)
for entry in someset:
trythemall(someset - set([entry]))
trythemall(allofthem)
Not hard to reorg if you want smallest subsets first, of course.
Is this what you are after (psuedocode)?
set = new List()
foreach (file in dir) {
set.add(file)
foreach (entry in set) {
do-test(set, entry)
}
}
This would build a set, then pass the set and each entry in the set to a do-test
method.
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