NewCalendar.scala

object NewCalendar extends App {

  def numberOfLines(totalMonths: Long, dayPerMonth: Int, dayPerWeek: Int): Long = {
    @annotation.tailrec
    def gcd(p: Int, q: Int): Int = if (q==0) p else gcd(q, p%q)
    val lcm = dayPerMonth / gcd(dayPerMonth, dayPerWeek) * dayPerWeek
    val (q, r) = (totalMonths / lcm, totalMonths % lcm)


    //println(gcd(dayPerMonth, dayPerWeek), lcm, q, r)

    val (rth, last, offset) = ((0, 0, 0) /: (1 to lcm)) {
      case ((rth, last, offset), i) =>
        //println(i, rth, last, offset)
        val (q1, r1) = ((offset + dayPerMonth)/dayPerWeek, (offset + dayPerMonth)% dayPerWeek)
        val ans = last + q1 + (if (r1==0) 0 else 1)
        ((if (i==r) ans else rth),  ans, r1)
    }

    q * last + rth
  }

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

  val filename = "A-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()
  }
}

NewCalendarTest.scala

import org.scalatest._

import NewCalendar._

class NewCalendarTest extends FunSuite with Matchers {

  test("sample #1") {
    assert(numberOfLines(3, 11, 4) === 11)
  }

  test("sample #2") {
    assert(numberOfLines(12, 28, 7) === 48)
  }

  test("small #17") {
    assert(numberOfLines(17, 1, 8) === 17)
  }

  test("sample case") {
    val input = """3
3 11 4
12 28 7
10 35 10""".lines

    val expected = """Case #1: 11
Case #2: 48
Case #3: 40""".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-practice.out").getLines()

    lineComparison(input, expected)
  }

  ignore("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.")
  }

}