DataPacking.scala

object DataPacking extends App {

  def minDisc(capacity: Int, files: Seq[Int]): Int = {

    @annotation.tailrec
    def loop(sorted: Vector[Int], count: Int): Int =
      if (sorted.size <= 1) sorted.size + count
      else {
        val (front, end) = sorted.init.span(_ <= capacity - sorted.last)
        loop(if (front.isEmpty) end else front.init ++ end, count + 1)
      }

    loop(files.sorted.toVector, 0)

  }

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

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

}

DataPackingTest.scala

import org.scalatest._

import DataPacking._

class DataPackingTest extends FunSuite {

  test("sample #1") {
    assert(minDisc(100, Seq(10, 20, 70)) === 2)
  }
  
  test("sample #2") {
    assert(minDisc(100, Seq(30, 40, 60, 70)) === 2)
  }
  
  test("sample #3") {
    assert(minDisc(100, Seq(10, 20, 30, 40, 60)) === 3)
  }
  
  test("sample case") {
    val input = """3
3 100
10 20 70
4 100
30 40 60 70
5 100
10 20 30 40 60""".lines

    val expected = """Case #1: 2
Case #2: 2
Case #3: 3""".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.out.ref").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.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.")
  }

}