Obtaining a powerset of a set in Java

Question

The powerset of {1, 2, 3} is:

{{}, {2}, {3}, {2, 3}, {1, 2}, {1, 3}, {1, 2, 3}, {1}}

Let\'s say I have a Set in Java:<

Answer 1

Actually, I've written code that does what you're asking for in O(1). The question is what you plan to do with the Set next. If you're just going to call size() on it, that's O(1), but if you're going to iterate it that's obviously O(2^n).

contains() would be O(n), etc.

Do you really need this?

EDIT:

This code is now available in Guava, exposed through the method Sets.powerSet(set).