CountingSheep.scala

object CountingSheep extends App {

  def lastNumber(n: Int): Option[Int] =
    if (n == 0) None
    else Some {
      Stream.from(1).scanLeft(Set.empty[Char]){
        (acc, i) => acc ++ (n * i).toString().toSet
      }.zipWithIndex.dropWhile(_._1 != ('0' to '9').toSet).head._2 * n

      /*
      @annotation.tailrec
      def loop(i: Int, acc: Set[Char]): Int = {
        val acc0 = acc ++ (n * i).toString().toSet
        if (acc0 == ('0' to '9').toSet) n * i
        else loop(i + 1, acc0)
      }
      loop(1, Set.empty)
       */
    }

  def process(lineIn: Iterator[String])(lineOut: String => Unit) =
    for (i <- 1 to lineIn.next().toInt) {
      lineOut(s"Case #$i: ${lastNumber(lineIn.next().toInt) getOrElse "INSOMNIA"}")
    }

  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()
  }
}

CountingSheepTest.scala

import org.scalatest._

import CountingSheep._

class CountingSheepTest extends FunSuite with Matchers {

  test("sample #1") {
    assert(lastNumber(0) === None)
  }

  test("sample #2") {
    assert(lastNumber(1) === Some(10))
  }

  test("sample #3") {
    assert(lastNumber(2) === Some(90))
  }

  test("sample #4") {
    assert(lastNumber(11) === Some(110))
  }

  test("sample #5") {
    assert(lastNumber(1692) === Some(5076))
  }

  test("sample case") {
    val input = """5
0
1
2
11
1692""".lines

    val expected = """Case #1: INSOMNIA
Case #2: 10
Case #3: 90
Case #4: 110
Case #5: 5076""".lines

    lineComparison(input, expected)
  }

  test("full small case") {
    val input = io.Source.fromFile("A-small-practice.in").getLines()
    val expected = io.Source.fromFile("A-small-practice.out").getLines()

    lineComparison(input, expected)
  }

  test("full large case") {
    val input = io.Source.fromFile("A-large-practice.in").getLines()
    val expected = io.Source.fromFile("A-large-practice.out").getLines()

    lineComparison(input, expected)
  }

  def lineComparison(input: Iterator[String], expected: Iterator[String]): Unit = {
    process(input) { s =>
      for (line <- s.lines) assert(line.trim === expected.next().trim)
    }
    assert(expected.hasNext === false, "Finished too fast.")
  }

}