diff -r 663c2a9108d1 -r 4de31fdc0d67 testing3/knight2.scala
--- a/testing3/knight2.scala	Sun Nov 01 01:21:31 2020 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,94 +0,0 @@
-// Part 3 about finding a single tour using the Warnsdorf Rule
-//=============================================================
-
-object CW8b {
-
-type Pos = (Int, Int)
-type Path = List[Pos]
-
-
-// for measuring time in the JAR
-def time_needed[T](code: => T) : T = {
-  val start = System.nanoTime()
-  val result = code
-  val end = System.nanoTime()
-  println(f"Time needed: ${(end - start) / 1.0e9}%3.3f secs.")
-  result
-}
-
-
-def print_board(dim: Int, path: Path): Unit = {
-  println
-  for (i <- 0 until dim) {
-    for (j <- 0 until dim) {
-      print(f"${path.reverse.indexOf((i, j))}%4.0f ")
-    }
-    println
-  } 
-}
-
-def add_pair(x: Pos, y: Pos): Pos = 
-  (x._1 + y._1, x._2 + y._2)
-
-def is_legal(dim: Int, path: Path, x: Pos): Boolean = 
-  0 <= x._1 && 0 <= x._2 && x._1 < dim && x._2 < dim && !path.contains(x)
-
-def moves(x: Pos): List[Pos] = 
-  List(( 1,  2),( 2,  1),( 2, -1),( 1, -2),
-       (-1, -2),(-2, -1),(-2,  1),(-1,  2)).map(add_pair(x, _))
-
-def legal_moves(dim: Int, path: Path, x: Pos): List[Pos] = 
-  moves(x).filter(is_legal(dim, path, _))
- 
-def ordered_moves(dim: Int, path: Path, x: Pos): List[Pos] = 
-  legal_moves(dim, path, x).sortBy((x) => legal_moves(dim, path, x).length)
-
-import scala.annotation.tailrec
-
-@tailrec
-def first(xs: List[Pos], f: Pos => Option[Path]): Option[Path] = xs match {
-  case Nil => None
-  case x::xs => {
-    val result = f(x)
-    if (result.isDefined) result else first(xs, f)
-  }
-}
-
-
-def tfirst_closed_tour_heuristics(dim: Int, path: Path): Option[Path] = {
-  if (path.length == dim * dim && moves(path.head).contains(path.last)) Some(path)
-  else
-    first(ordered_moves(dim, path, path.head), (x: Pos) => tfirst_closed_tour_heuristics(dim, x::path))
-}
-
-def first_closed_tour_heuristics(dim: Int, path: Path) =
- time_needed(tfirst_closed_tour_heuristics(dim: Int, path: Path))
-
-def first_closed_tour_heuristic(dim: Int, path: Path) =
- time_needed(tfirst_closed_tour_heuristics(dim: Int, path: Path))
-
-
-// heuristic cannot be used to search for closed tours on 7 x 7 an beyond
-//for (dim <- 1 to 6) {
-//  val t = time_needed(0, first_closed_tour_heuristics(dim, List((dim / 2, dim / 2))))
-//  println(s"${dim} x ${dim} closed: " + (if (t == None) "" else { print_board(dim, t.get) ; "" }))
-//}
-
-
-def tfirst_tour_heuristics(dim: Int, path: Path): Option[Path] = {
-  if (path.length == dim * dim) Some(path)
-  else
-    first(ordered_moves(dim, path, path.head), (x: Pos) => tfirst_tour_heuristics(dim, x::path))
-}
-
-
-def first_tour_heuristics(dim: Int, path: Path) = 
-  time_needed(tfirst_tour_heuristics(dim: Int, path: Path))
-
-def first_tour_heuristic(dim: Int, path: Path) = 
-  time_needed(tfirst_tour_heuristics(dim: Int, path: Path))
-
-// will be called with boards up to 30 x 30
-
-
-}