* element ended up at.
     */
    @CanIgnoreReturnValue
    int bubbleUpAlternatingLevels(int index, E x) {
      while (index > 2) {
        int grandParentIndex = getGrandparentIndex(index);
        E e = elementData(grandParentIndex);
        if (ordering.compare(e, x) <= 0) {
          break;
        }
        queue[index] = e;
        index = grandParentIndex;
      }