ReverseWords.scala

object ReverseWords extends App {

  def reverse(line: String): String = line.split(' ').reverse mkString " "

  def reverse2(line: String): String = {
    def reverse(ss: List[String]): String = ss match {
      case Nil      => ""
      case x :: Nil => x
      case x :: xs  => reverse(xs) + " " + x
    }
    reverse((line split ' ').toList)
  }

  def reverse3(line: String): String = {
    def reverseList(ss: List[String], acc: List[String] = Nil): List[String] = ss match {
      case Nil     => acc
      case x :: xs => reverseList(xs, x :: acc)
    }
    reverseList(line.split(' ').toList) mkString " "
  }

  def reverse4(line: String): String =
    (List.empty[String] /: line.split(' '))((acc, s) => s :: acc) mkString " "

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

  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()
  }
}

SmoothingWindowTest.scala

import org.scalatest._

import ReverseWords._

class SmoothingWindowTest extends FunSuite {

  test("sample #1") {
    assert(reverse("this is a test") === "test a is this")
  }
  
  test("sample case") {
    val input = """3
this is a test
foobar
all your base""".lines

    val expected = """Case #1: test a is this
Case #2: foobar
Case #3: base your all""".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.")
  }

}