A solver using Scala's for-yield syntax to solve the Johnny Hates Math problem found at http://www.spoj.com/problems/ANARC07J/ (NB: this is to find all solutions to the problem, not to satisfy the SPOJ IO specification)

SolverUsingFor.scala

package jhm

case class SolverUsingFor( digits: String, total: Int, maxDigitsPerNumber: Int = 5
                    ) extends JHMSolver(digits, total, maxDigitsPerNumber) {

  override def solve(digits: String, total: Int, maxDigitsPerNumber: Int = 5): List[List[Int]] = for {
    leftCount <- (1 to maxDigitsPerNumber).toList
    if leftCount <= digits.length
    (leftStr, rightStr) = digits.splitAt(leftCount)
    if (leftCount == 1 || leftStr(0) != '0')  // No numbers may start with '0' (except zero)
    left = leftStr.toInt
    if (left < total && rightStr != "") || (left == total && rightStr.replace("0","") == "")
    // Still going, or reached the target sub-total with no remaining text to match except maybe zeroes
    solution <- if (left == total && rightStr == "") List(List(left))
    else solve(rightStr, total - left) map (left :: _)
  } yield solution

}