PascalTriangle.scala

object Test {
  type R = BigInt

  def main(av:Array[String]):Unit = {
    //timed{ pascal(0, av.head.toInt) }
    timed{ pascalV2(av.head.toInt) }
  }

  import collection.parallel.mutable.{ParArray => Array}

  val zero = BigInt(0)

  def pascalV2(n:Int):Unit = (1 to n).foldLeft(Array(1:R)){ case (acc, e) =>
    //println(acc mkString " ")
    (acc :+ zero).zip(zero +: acc).map{ case (l,r) => l + r }
  }

  def updateLine(line:Array[R]): Array[R] = {
    val newline = BigInt(1) +: (line zip line.tail).map(t => t._1 + t._2) :+ BigInt(1)
    //println(line mkString " ")
    newline
  }

  def pascal(c:Int, r:Int)(implicit line:Array[R] = Array(1)): R =
    if (0 < r) pascal(c, r-1)(updateLine(line)) else { updateLine(line); line(c) }

  def timed[T](f: => T) = {
    val s = System.currentTimeMillis
    f
    val e = System.currentTimeMillis
    println(s"Done in ${(e-s)/1000.0} s")
  }

}