StandingOvation.scala

object StandingOvation extends App {
  def toList(str: String): List[Int] = {
    str.toCharArray.map(_ - '0').toList
  }

  def solve(people: String): Int = {
    @annotation.tailrec
    def solveInner(people: List[(Int, Int)], standing: Int, invite: Int): Int = {
      val shy = people.head._1
      val level = people.head._2
      if (level == 0) people match {
        case head :: Nil => 0
        case _ => solveInner(people.tail, shy, 0)
      }
      else people match {
        case Nil => -1
        case head :: Nil => {
          if (level <= standing) invite
          else invite + (level - standing)
        }
        case head :: tail => {
          if (level <= standing) solveInner(tail, standing + shy, invite)
          else {
            val toInvite = level - standing
            solveInner(tail, standing + shy + toInvite, invite + toInvite)
          }
        }
      }
    }
    solveInner(toList(people).zipWithIndex, 0, 0)
  }

  def process(lineIn: Iterator[String])(lineOut: String => Unit) =
    for (i <- 1 to lineIn.next().toInt) {
      val Array(max, people) = lineIn.next().split(" ")
      lineOut(s"Case #$i: ${solve(people)}")
    }

  val filename = "A-large-practice"
  val writer = new java.io.PrintWriter(filename + ".out")
  try {
    process(io.Source.fromFile(filename + ".in").getLines) { s =>
      writer.println(s); writer.flush()
    }
  } finally {
    writer.flush(); writer.close()
  }
}