2016 Update

Task/N-queens-problem/Scala/n-queens-problem-1.scala

@@ -14,7 +14,3 @@ def expand(solutions: Iterator[List[Pos]], size: Int, row: Int) =
     pos <- rowSet(size, row)
     if solution forall (_ legal pos)
   } yield pos :: solution
-
-def seed(size: Int) = rowSet(size, 0) map (sol => List(sol))
-
-def solve(size: Int) = (1 until size).foldLeft(seed(size)) (expand(_, size, _))

Task/N-queens-problem/Scala/n-queens-problem-2.scala

@@ -0,0 +1,18 @@
+def vecOk(v: IndexedSeq[Int])(f: (Int,Int) => Int): Boolean = {
+  def vecOkIter(level: Int)(lst: List[Int]): Boolean = {
+    if (level > -1) {
+      val d = f(v(level),level)
+      if (lst.contains(d)) false
+      else vecOkIter(level-1)(d :: lst)
+    }
+    else true
+  }
+  vecOkIter(v.length-1)(List[Int]())
+}
+
+def nQueen(n: Int) = for (
+  v <- (1 to n).permutations
+  if vecOk(v)(_+_) && vecOk(v)(_-_)
+) yield v
+
+nQueen(8)