Data commit

Task/Ranking-methods/Scala/ranking-methods.scala

@@ -0,0 +1,44 @@
+object RankingMethods extends App {
+    case class Score(score: Int, name: String) // incoming data
+    case class Rank[Precision](rank: Precision, names: List[String]) // outgoing results (can be int or double)
+    case class State[Precision](n: Int, done: List[Rank[Precision]]) { // internal state, no mutable variables
+        def next(n: Int, next: Rank[Precision]) = State(n, next :: done)
+    }
+    def grouped[Precision](list: List[Score]) = // group names together by score, with highest first
+        (scala.collection.immutable.TreeMap[Int, List[Score]]() ++ list.groupBy(-_.score))
+        .values.map(_.map(_.name)).foldLeft(State[Precision](1, Nil)) _
+
+    // Ranking methods:
+
+    def rankStandard(list: List[Score]) =
+        grouped[Int](list){case (state, names) => state.next(state.n+names.length, Rank(state.n, names))}.done.reverse
+
+    def rankModified(list: List[Score]) =
+        rankStandard(list).map(r => Rank(r.rank+r.names.length-1, r.names))
+
+    def rankDense(list: List[Score]) =
+        grouped[Int](list){case (state, names) => state.next(state.n+1, Rank(state.n, names))}.done.reverse
+
+    def rankOrdinal(list: List[Score]) =
+        list.zipWithIndex.map{case (score, n) => Rank(n+1, List(score.name))}
+
+    def rankFractional(list: List[Score]) =
+        rankStandard(list).map(r => Rank((2*r.rank+r.names.length-1.0)/2, r.names))
+
+    // Tests:
+
+    def parseScores(s: String) = s split "\\s+" match {case Array(s,n) => Score(s.toInt, n)}
+    val test = List("44 Solomon", "42 Jason", "42 Errol", "41 Garry", "41 Bernard", "41 Barry", "39 Stephen").map(parseScores)
+
+    println("Standard:")
+    println(rankStandard(test) mkString "\n")
+    println("\nModified:")
+    println(rankModified(test) mkString "\n")
+    println("\nDense:")
+    println(rankDense(test) mkString "\n")
+    println("\nOrdinal:")
+    println(rankOrdinal(test) mkString "\n")
+    println("\nFractional:")
+    println(rankFractional(test) mkString "\n")
+
+}