code: public ArrayList<Integer> getVisited() {
      if (0 == (this.registry.length - this.unvisitedCount)) {
        return new ArrayList<Integer>();
      }
      ArrayList<Integer> res = new ArrayList<Integer>(this.registry.length - this.unvisitedCount);
      for (int i = 0; i < this.registry.length; i++) {
        if (ONE == this.registry[i]) {
          res.add(i);
        }
      }
      return res;
    }
docs: Get the list of visited positions. Returns NULL if none are visited.
  
  @return list of visited positions.