所持金と支払価格から、お釣りが最小になる払い方を求める。

payment.scala

/**
 * do execute.
 * $ scala payment.scala {pocket} {price}
 */
object Main {
  
  implicit val coins = List(1, 5, 10, 50, 100, 500, 1000, 5000, 10000)
  
  def main(args: Array[String]): Unit = {
    if (args.length != 2) sys.exit(-1)
    
    val Array(pocket, price) = args.map(_.toInt)
    
    if (pocket < price) sys.exit(-1)
    
    val payment = getNumberOfCoinsOfPayment(pocket, price)
    (coins zip payment).foreach(println)
  }
  
  def getNumberOfCoinsOfPayment(pocket: Int, price: Int): List[Int] = (getNumberOfCoins(pocket), getNumberOfCoins(pocket - price)).zipped.map(_-_).map(minusToZero)
  
  def getNumberOfCoins(money: Int)(implicit coins: List[Int]): List[Int] = (coins :\ (money, List[Int]())) {case (c, (b, list)) => (b % c, (b / c) :: list)}._2
  
  def minusToZero(n: Int): Int = if (n > 0) n else 0
}