An evaluation of the educational effectiveness of a didactic method for the active learning of greedy algorithms is presented. The didactic method sets students structured-inquiry challenges to be addressed with a specific experimental method, supported by the interactive system GreedEx. This didactic method has been refined over several years of use. Additional elements are lecture contents and the scheduling of classes and lab sessions. Learning gain in the topic of greedy algorithms was measured in the short term for two groups of students: an experimental group taught with the new didactic method, and a control group taught with a traditional approach. The results show a significant learning gain improvement in the experimental group, while the students taught with a traditional method had little learning gain. In addition, the levels of Bloom's taxonomy at which improvements occurred were identified. In the control group, improvements were found at the knowledge level. In the experimental group, however, improvements were found at the knowledge and the comprehension levels, although not at the analysis level. These results are encouraging and indicate directions for future research, as analysis skills are important in algorithm courses.