Technical note : A note on the complexity of family scheduling to minimize the number of late jobs

The single-machine family scheduling problem of minimizing the number of late jobs has been known to be NP-hard, but whether it is NP-hard in the strong sense is cited as an open problem in several reviews. In this note, we prove that this problem is strongly NP-hard even if all set-up times and processing times are one unit.Department of Logistics and Maritime Studie