tessf.scala

val cost = 5
val bills = List(1, 2, 5, 10, 20, 50)
val bounds: Map[Int, Int] = bills.map(bill => bill -> Math.floor(cost / bill).toInt).toMap
lazy val betterBounds = bounds.map { case (bill, bound) =>
bill -> (0 to bound).map(currBound => List.fill(currBound)(bill)).toList
}
println((0 to cost).map(n => betterBounds.values.toList.flatten.flatten.combinations(n)).toList.flatten.count(_.sum == cost))