cover

type Instance struct {
	// The number of elements in the set X to be covered, indexed
	// 0 ... M-1.
	M int
	// Subsets of X. The inner slices must only contain element indices in
	// [0, M-1]. The indices must be sorted and each subset must be include
	// at most once. Empty Subsets are not allowed.
	Subsets [][]int
	// The cost of each subset. Each cost must be strictly positive.
	// The length of subsets and Costs must be equal.
	// The restrictions on the Costs reasonable for many problems and
	// suit certain algorithms.
	Costs []float64
}