Merge pull request #235 from adrianobrito/dijkstra-scala

Adicionar Algoritmo de Dijkstra em Scala

Author: kelvins

README.md

@@ -112,8 +112,8 @@ Com o objetivo de alcançar uma abrangência maior e encorajar mais pessoas a co
   </a>
   </td>
   <td> <!-- Scala -->
-  <a href="./CONTRIBUTING.md">
-  <img align="center" height="25" src="./logos/github.svg" />
+  <a href="./src/scala/Dijkstra.scala">
+  <img align="center" height="25" src="./logos/scala.svg" />
   </a>
   </td>
   <td> <!-- Kotlin -->

src/scala/Dijkstra.scala

@@ -0,0 +1,62 @@
+import scala.annotation.tailrec
+
+trait Path {
+ def edges: Seq[Edge]
+}
+
+case class ExistingPath(edges: Seq[Edge]) extends Path
+
+object EmptyPath extends Path {
+ override def edges: Seq[Edge] = Seq.empty
+}
+
+case class Vertex(id: String)
+
+case class Edge(from: Vertex, to: Vertex, distance: Int)
+
+case class Graph(edges: List[Edge]) {
+
+ implicit object EdgesOrdering extends Ordering[Edge] {
+ def compare(a: Edge, b: Edge) = a.distance compare b.distance
+ }
+
+ @tailrec
+ final def dijkstra(start: Vertex, pathComposition: Path = EmptyPath): Path = {
+ val startEdges: Seq[Edge] = edges.filter(_.from == start).sorted
+ val smallestDistance: Option[Edge] = startEdges
+ .filter(e => !pathComposition.edges.map(_.from).contains(e.to))
+ .headOption
+
+ smallestDistance match {
+ case Some(distance) =>
+ dijkstra(
+ distance.to,
+ ExistingPath(edges = pathComposition.edges.appended(distance))
+ )
+ case None => pathComposition
+ }
+ }
+}
+
+object Main extends App {
+
+ val startA: Vertex = Vertex("A")
+ val graph: Graph = Graph(
+ edges = List(
+ Edge(from = Vertex("A"), to = Vertex("B"), distance = 1),
+ Edge(from = Vertex("A"), to = Vertex("C"), distance = 4),
+ Edge(from = Vertex("B"), to = Vertex("A"), distance = 1),
+ Edge(from = Vertex("B"), to = Vertex("C"), distance = 2),
+ Edge(from = Vertex("B"), to = Vertex("D"), distance = 5),
+ Edge(from = Vertex("C"), to = Vertex("A"), distance = 4),
+ Edge(from = Vertex("C"), to = Vertex("B"), distance = 2),
+ Edge(from = Vertex("C"), to = Vertex("D"), distance = 1),
+ Edge(from = Vertex("D"), to = Vertex("B"), distance = 5),
+ Edge(from = Vertex("D"), to = Vertex("C"), distance = 1)
+ )
+ )
+
+ val result: Path = graph.dijkstra(start = startA)
+ println("Calculating path...")
+ println(s"Result: ${result.edges}")
+}