Fairland.scala

object Fairland extends App {
  def maxEmployee(n: Int, d: Int, sGen: (Int, Int, Int, Int), mGen: (Int, Int, Int, Int)): Int = {
    val map = Map.empty[Int, Int] withDefaultValue 0

    map(10)

    val dx = Seq((18, 1), (18 + 395, -1)).groupBy(_._1).mapValues(_.map(_._2).sum).toSeq.sorted

    ((0, 0) /: dx) {
      case ((current, max), (x, d)) =>
        val next = current + d
        (next, max max next)
    }._2
  }
}

FairlandTest.scala

import org.scalatest._

import Fairland._

class FairlandTest extends FunSuite {

  test("sample #1") {
    assert(maxEmployee(1, 395, (18, 246, 615815, 60), (73, 228, 14618, 195)) === 1)
  }

  test("sample #2") {
    assert(maxEmployee(6, 5, (10, 1, 3, 17), (5, 2, 7, 19)) === 3)
  }

}