Stable Marriage with One-Sided Preference

Many countries around the world, including Korea, use the school choice lottery system. However, this method has a problem in that many students are assigned to less-preferred schools based on the lottery results. In addition, the task of finding a good assignment with ties often has a time complexity of NP, making it a very difficult problem to improve the quality of the assignment. In this paper, we prove that the problem of finding a stable matching that maximizes the student-oriented preference utility in a two-sided market with one-sided preference can be solved in polynomial time, and we verify through experiments that the quality of assignment is improved. The main contributions of this paper are as follows. We found that stable student-oriented allocation in a two-sided market with one-sided preferences is the same as stable allocation in a two-sided market with symmetric preferences. In addition, we defined a method to quantify the quality of allocation from a preference utilitarian perspective. Based on the above two, it was proven that the problem of finding a stable match that maximizes the preference utility in a two-sided market with homogeneous preferences can be reduced to an allocation problem. In this paper, through an experiment, we quantitatively verified that optimal student assignment assigns more students to schools of higher preference, even in situations where many students are assigned to schools of low preference using the existing assignment method.