for (int i = 0; i < size; i++) {
          keys[i] = rng.nextInt();
        }
        return createTreap(Ints.asList(keys));
      }

      // See http://en.wikipedia.org/wiki/Treap for details on the algorithm.
      private Optional<BinaryNode> createTreap(List<Integer> keys) {
        if (keys.isEmpty()) {
          return Optional.absent();
        }
        int minIndex = 0;

        for (int i = 0; i < size; i++) {
          keys[i] = rng.nextInt();
        }
        return createTreap(Ints.asList(keys));
      }

      // See http://en.wikipedia.org/wiki/Treap for details on the algorithm.
      private Optional<BinaryNode> createTreap(List<Integer> keys) {
        if (keys.isEmpty()) {
          return Optional.absent();
        }
        int minIndex = 0;