Initial data commit

Task/Dijkstras-algorithm/Scala/dijkstras-algorithm-1.scala

@@ -0,0 +1,29 @@
+object Dijkstra {
+
+  type Path[Key] = (Double, List[Key])
+
+  def Dijkstra[Key](lookup: Map[Key, List[(Double, Key)]], fringe: List[Path[Key]], dest: Key, visited: Set[Key]): Path[Key] = fringe match {
+    case (dist, path) :: fringe_rest => path match {case key :: path_rest =>
+      if (key == dest) (dist, path.reverse)
+      else {
+        val paths = lookup(key).flatMap {case (d, key) => if (!visited.contains(key)) List((dist + d, key :: path)) else Nil}
+        val sorted_fringe = (paths ++ fringe_rest).sortWith {case ((d1, _), (d2, _)) => d1 < d2}
+        Dijkstra(lookup, sorted_fringe, dest, visited + key)
+      }
+    }
+    case Nil => (0, List())
+  }
+
+  def main(x: Array[String]): Unit = {
+    val lookup = Map(
+      "a" -> List((7.0, "b"), (9.0, "c"), (14.0, "f")),
+      "b" -> List((10.0, "c"), (15.0, "d")),
+      "c" -> List((11.0, "d"), (2.0, "f")),
+      "d" -> List((6.0, "e")),
+      "e" -> List((9.0, "f")),
+      "f" -> Nil
+    )
+    val res = Dijkstra[String](lookup, List((0, List("a"))), "e", Set())
+    println(res)
+  }
+}