UpAndDown.scala

object UpAndDown extends App {

  @annotation.tailrec
  def minSwap(ints: IndexedSeq[Int], count: Int = 0): Int =
    if (ints.isEmpty) count
    else {
      val minIndex = ints.zipWithIndex.min._2
      val (left, right) = ints splitAt minIndex
      minSwap(left ++ right.tail, count + (left.size min right.tail.size))
    }

  def process(lineIn: Iterator[String])(lineOut: String => Unit) =
    for (i <- 1 to lineIn.next().toInt) {
      val n = lineIn.next().toInt
      val ints = lineIn.next().split(' ').map(_.toInt)
      lineOut(s"Case #$i: ${minSwap(ints)}")
    }

  val filename = "B-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()
  }

}

UpAndDownTest.scala

import org.scalatest._

import UpAndDown._

class UpAndDownTest extends FunSuite {

  test("sample #1") {
    assert(minSwap(Vector(1,2,3)) === 0)
  }
  
  test("sample #2") {
    assert(minSwap(Vector(1,8,10,3,7)) === 1)
  }
  
  test("sample case") {
    val input = """2
3
1 2 3
5
1 8 10 3 7""".lines

    val expected = """Case #1: 0
Case #2: 1""".lines

    lineComparison(input, expected)
  }

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

    lineComparison(input, expected)
  }

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

    lineComparison(input, expected)
  }

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

}