The AAM problem is typically modeled as the maximum common edge subgraph (MCES) problem between the molecular graphs of reactants (R) and products (P ). The MCESs between R and P are the common substructures that maximize the number of edges (bonds) shared by the reactant and product graphs. In other words, the MCESs consist of chemical bonds that likely to be preserved during the reaction, maximizing the number of such unchanged bonds (or equivalently, minimizing the number of bonds broken or formed).