Hi,

I want to compute the cartesian product of an arbitrary number of nonempty sets in Java.

I've wrote that iterative code...

public static <T> List<Set<T>> cartesianProduct(List<Set<T>> list) {
	List<Iterator<T>> iterators = new ArrayList<Iterator<T>>(list.size());
	List<T> elements = new ArrayList<T>(list.size());
	List<Set<T>> toRet = new ArrayList<Set<T>>();
	for (int i = 0; i < list.size(); i++) {
		iterators.add(list.get(i).iterator());
		elements.add(iterators.get(i).next());
	}
	for (int j = 1; j >= 0;) {
		toRet.add(Sets.newHashSet(elements));
		for (j = iterators.size()-1; j >= 0 && !iterators.get(j).hasNext(); j--) {
			iterators.set(j, list.get(j).iterator());
			elements.set(j, iterators.get(j).next());
		}
		elements.set(Math.abs(j), iterators.get(Math.abs(j)).next());
	}
	return toRet;
}

...but I found it rather inelegant. Someone has a better, still iterative solution? A solution that uses some wonderful functional-like approach? Otherwise... suggestion about how to improve it? Errors?

Thanks :)