In this paper a greedy algorithm for some variants of the sequencing by hybridization method is presented. In the standard version
of the method information about repetitions is not available. In the paper it is assumed that a partial information of this type is a part of the
problem instance. Here two simple but realistic models of this information are taken into consideration. The first one assumes it is known
if a given element of a spectrum appears in the target sequence once or more than once. The second model uses the knowledge if a given
element of a spectrum occurs in the analyzed sequence once, twice or at least three times. The proposed greedy algorithm solves the variant
of the problem with positive and negative errors. Results of a computational experiment are reported which, among others, confirm that
the additional information leads to the improvement of the obtained solutions. They also show that the more precise model of information
increases the quality of reconstructed sequences.