Monday, February 14, 2011

I whine too much.

Mea culpa.
   ...
   for (Foo foo : permute(fooList)) {
        operateOnFoo (foo);
    }
   ...

  private static final Random rng = new Random();

  private static <E> List<E> permute (List<E> list) {
    List<E> answer = Lists.newArrayList (list);
    Collections.shuffle (answer, rng);
    return answer;
  }
at

2 comments:

  1. Holger DürerFebruary 15, 2011 at 8:32 AM

    But is that the implementation people would expect? If I read permute I'd assume/hope for an implementation that will over subsequent n! (assuming distinct elements) calls enumerate all permutations of the collection.

    ReplyDelete
  2. Joe MarshallFebruary 15, 2011 at 9:14 AM

    That's why it is private and static.

    If you really thought that, wouldn't you expect a two-argument version that allowed you to select which of the n! permutations?

    ReplyDelete