2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/151970The purpose of this note is to attach a name to a natural class of combinatorial problems and to point out that this class includes many important special cases. We also show that a simple problem of placing nonoverlapping labels on a rectangular map is NP-complete.Data Structures and AlgorithmsCombinatoricstext