PartiallyCompleteGraph.scala

def selectEdges(nv: Int = 18, ne: Int = 12) = {
  var m  = Map.empty[Int, Set[Int]] withDefaultValue Set.empty
  val vr = (1 to nv)
  vr.reverse.foreach { v =>
    val s0 = m(v)
    val cand0 = vr.filterNot(s0.contains)
    val cand1 = cand0.filter { v2 => m(v2).size < ne }
    val tk    = ne - s0.size
    val cand = cand1.take(tk)
    assert (cand.size == tk, s"Woops. wanted $tk got ${cand.size}")
    val s1 = s0 ++ cand
    m = m + (v -> s1)
    cand.foreach { v2 =>
      val s2 = m(v2)
      val s3 = s2 + v
      m = m + (v2 -> s3)
    }
  }
  m
}