“…Shift and daysoff scheduling problems are equivalent when there is a single shift on a work day. Consequently, related problems are classified under single-shift scheduling (see, e.g., [13,27,5,15,28,37,9]) and multiple-shift scheduling (see, e.g., [56,47,14,39,38]) of a single category or multiple categories of employees. There are other studies which consider employee preferences and hierarchy.…”