code: public static long[] getUSmilesNumbers(IAtomContainer container) throws CDKException {
          String aux = auxInfo(container, INCHI_OPTION.RecMet, INCHI_OPTION.FixedH);
          return parseUSmilesNumbers(aux, container);
      }
docs: Obtain the InChI numbers for the input container to be used to order
  atoms in Universal SMILES {@cdk.cite OBoyle12}. The numbers are obtained
  using the fixedH and RecMet options of the InChI. All non-bridged
  hydrogens are labelled as 0.
  
  @param container the structure to obtain the numbers of
  @return the atom numbers
  @throws CDKException