On the completeness of a generalized matching problem
David G. Kirkpatrick, Pavol Hell · 1978
A perfect matching in a graph H may be viewed as a collection of subgraphs of H, each of which is isomorphic to K2, whose vertex sets partition the vertex set of H. This is naturally generalized by replacing K2 by an arbitrary graph G. We show that if G contains a component with at least three vertices then this generalized matching problem is NP-complete. These generalized matchings have numerous applications including the minimization of second-order conflicts in examination scheduling.