KingdomRush.scala

object KingdomRush extends App {

  def loop(levels: Seq[(Int, Int)], partials: Seq[(Int, Int)], currentStar: Int, acc: Int): Option[Int] = {
    
    println(levels, partials, currentStar, acc)
    
    if (levels.isEmpty) Some(acc)
    else {
      val (clearable, unclearable) = levels.partition(_._2 <= currentStar)

      if (clearable.nonEmpty) {

        loop(clearable.tail ++ unclearable, partials, currentStar + 2, acc + 1)
      } else {

        val (clearablePartial, unclearablePartial) = partials.partition(_._2 <= currentStar)

        if (clearablePartial.nonEmpty) {
          loop(levels, clearablePartial.tail ++ unclearablePartial, currentStar + 1, acc + 1)
        } else {

          val (firstClearable, firstUnclearable) = levels.partition(_._1 <= currentStar)

          if (firstClearable.nonEmpty) {
            loop(firstClearable.tail ++ firstUnclearable, partials :+ firstClearable.head, currentStar + 1, acc + 1)
          } else None

        }

      }
    }

  }

  def minNumberOfLevels(levels: Seq[(Int, Int)]): Option[Int] = {
    loop(levels, Seq(), 0, 0)
  }

  def process(lineIn: Iterator[String])(lineOut: String => Unit) =
    for (i <- 1 to lineIn.next().toInt) {
      val n = lineIn.next().toInt
      val levels = Seq.fill(n) {
        val Array(a, b) = lineIn.next() split ' ' map (_.toInt)
        (a, b)
      }
      lineOut(s"Case #$i: ${minNumberOfLevels(levels) getOrElse "Too Bad"}")
    }

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

}

KingdomRushTest.scala

import org.scalatest._

import KingdomRush._

class KingdomRushTest extends FunSuite {

  test("loop #1") {
    assert(loop(Seq(), Seq(), 4, 3) === Some(3))
  }

  test("loop #2") {
    assert(loop(Seq((0, 2)), Seq(), 2, 2) === Some(3))
  }

  test("loop #3") {
    assert(loop(Seq((0, 2)), Seq((0, 1)), 1, 1) === Some(3))
  }

  test("loop #4") {
    assert(loop(Seq((0, 1), (0, 2)), Seq(), 0, 0) === Some(3))
  }

  test("sample #1") {
    assert(minNumberOfLevels(Seq((0, 1), (0, 2))) === Some(3))

  }

  test("sample #2") {
    assert(minNumberOfLevels(Seq((2, 2), (0, 0), (4, 4))) === Some(3))

  }

  test("sample #3") {
    assert(minNumberOfLevels(Seq((1, 1))) === None)

  }

  test("sample #4") {
    assert(minNumberOfLevels(Seq((0, 5), (0, 1), (1, 1), (4, 7), (5, 6))) === Some(6))
  }
  
  test("small #5") {
    val input = """1
9
6 9
14 18
3 14
0 0
2 9
7 13
5 7
4 5
7 14""".lines

    val expected = """Case #1: Too Bad""".lines

    lineComparison(input, expected)
  }
  
  test("sample case") {
    val input = """4
2
0 1
0 2
3
2 2
0 0
4 4
1
1 1
5
0 5
0 1
1 1
4 7
5 6""".lines

    val expected = """Case #1: 3
Case #2: 3
Case #3: Too Bad
Case #4: 6""".lines

    lineComparison(input, expected)
  }

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

    lineComparison(input, expected)
  }

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

}