Data commit

Task/24-game-Solve/Scala/24-game-solve.scala

@@ -0,0 +1,25 @@
+def permute(l: List[Double]): List[List[Double]] = l match {
+  case Nil => List(Nil)
+  case x :: xs =>
+    for {
+      ys <- permute(xs)
+      position <- 0 to ys.length
+      (left, right) = ys splitAt position
+    } yield left ::: (x :: right)
+}
+
+def computeAllOperations(l: List[Double]): List[(Double,String)] = l match {
+  case Nil => Nil
+  case x :: Nil => List((x, "%1.0f" format x))
+  case x :: xs =>
+    for {
+      (y, ops) <- computeAllOperations(xs)
+      (z, op) <-
+        if (y == 0)
+          List((x*y, "*"), (x+y, "+"), (x-y, "-"))
+        else
+          List((x*y, "*"), (x/y, "/"), (x+y, "+"), (x-y, "-"))
+    } yield (z, "(%1.0f%s%s)" format (x,op,ops))
+}
+
+def hasSolution(l: List[Double]) = permute(l) flatMap computeAllOperations filter (_._1 == 24) map (_._2)