RopeIntranet.scala

object RopeIntranet {
  def main(args: Array[String]) {
    val writer = new java.io.PrintWriter("a-large.out")
    try {
      process(io.Source.fromFile("A-large-practice.in").getLines)(writer.println)
    } finally {
      writer.flush()
      writer.close()
    }
  }
  
  def process(lineIn: Iterator[String])(lineOut: String => Unit) = {
    for (i <- 1 to lineIn.next().toInt) {
      val ropes = for (j <- 1 to lineIn.next().toInt) yield {
        val Array(lhs, rhs) = lineIn.next().split(" ").map(_.toInt)
        (lhs, rhs)
      }
      lineOut(s"Case #$i: ${countRopes(ropes.toList, 0)}")
    }
  }
  
  def isCrossed(lhs: (Int, Int), rhs: (Int, Int)): Boolean =
    (lhs._1 - rhs._1) * (lhs._2 - rhs._2) < 0
  
  def countCrossing(rope: (Int, Int), ropes: List[(Int, Int)]): Int =
    ropes.filter(isCrossed(_, rope)).length
  
  @annotation.tailrec  
  def countRopes(ropes: List[(Int, Int)], count: Int): Int = {
    if (ropes.length < 2) count
    else {
      val count1 = countCrossing(ropes.head, ropes.tail)
      countRopes(ropes.tail, count + count1)
    }
  }
}