FileFixIt.scala

object FileFixIt extends App {

  def subsetdir(input: String): Set[String] =
    (input split '/' drop 1).foldLeft(("", Set.empty[String])) {
      case ((current, acc), dir) =>
        val d = s"$current/$dir"
        (d, acc + d)
    }._2

  def numOfMkdir(exists: Set[String], todo: Set[String]): Int =
    ((todo flatMap subsetdir) -- (exists flatMap subsetdir)).size

  def process(lineIn: Iterator[String])(lineOut: String => Unit) =
    for (i <- 1 to lineIn.next().toInt) {
      def readFiles(n: Int) = Seq.fill(n)(lineIn.next()).toSet
      val Array(n, m) = lineIn.next().split(' ').map(_.toInt)
      val exists = readFiles(n)
      val todo = readFiles(m)

      lineOut(s"Case #$i: ${numOfMkdir(exists, todo)}")
    }

  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()
  }

}

FileFixItTest.scala

import org.scalatest._

import FileFixIt._

class FileFixItTest extends FunSuite {
  
  test("sample #1") {
    assert(numOfMkdir(Set.empty, Set("/home/gcj/finals", "/home/gcj/quals")) === 4)
  }
  
  test("sample #2") {
    assert(numOfMkdir(Set("/chicken", "/chicken/egg"), Set("/chicken")) === 0)
  }
  
  test("sample #3") {
    assert(numOfMkdir(Set("/a"), Set("/a/b", "/a/c", "/b/b")) === 4)
  }
  
  test("sample case") {
    val input = """3
0 2
/home/gcj/finals
/home/gcj/quals
2 1
/chicken
/chicken/egg
/chicken
1 3
/a
/a/b
/a/c
/b/b""".lines

    val expected = """Case #1: 4
Case #2: 0
Case #3: 4""".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)
  }
}