Jarvis march implementation scala

contents/jarvis_march/code/scala/jarvisMarch.scala

@@ -0,0 +1,60 @@
+object GiftWrap {
+
+  case class Point(x: Int, y: Int)
+
+  def jarvisMarch(gift: List[Point]): List[Point] = {
+
+    def isClockwise(p1: Point, p2: Point, p3: Point): Boolean =
+      (p3.y - p1.y) * (p2.x - p1.x) >= (p2.y - p1.y) * (p3.x - p1.x)
+
+    def leastClockwise(apex: Point)(a: Point, b: Point): Point =
+      if (!isClockwise(apex, a, b)) a else b
+
+    def nextPointOnHull(current: Point): Point =
+      gift
+        .filter(_ != current) //ignore current point
+        .reduce(leastClockwise(current))
+
+    def leftmost(points: List[Point]): Point =
+      points.reduce((a, b) => if (a.x < b.x) a else b)
+
+    def buildHull(hull: List[Point]): List[Point] =
+      nextPointOnHull(hull.last) match {
+        case backToStart if backToStart == hull.head => hull
+        case nextPoint                               => buildHull(hull :+ nextPoint)
+      }
+
+    buildHull(List(leftmost(gift))) // leftmost point guaranteed to be in hull
+
+  }
+
+  def main(args: Array[String]): Unit = {
+
+    val testGift = List(
+      (-5, 2),
+      (-13, 100),
+      (5, 7),
+      (-6, -12),
+      (-14, -14),
+      (9, 9),
+      (-1, -1),
+      (20, 20),
+      (-10, 11),
+      (-13, 10),
+      (-6, 15),
+      (-6, -8),
+      (15, -9),
+      (7, -7),
+      (-2, -9),
+      (15, -15),
+      (6, -5),
+      (0, 14),
+      (2, 8)
+    ).map({ case (x, y) => Point(x, y) })
+
+    val hull = jarvisMarch(testGift)
+
+    println("The points in the wrapping are:")
+    hull.foreach(println)
+  }
+}

contents/jarvis_march/jarvis_march.md

@@ -50,6 +50,8 @@ Since this algorithm, there have been many other algorithms that have advanced t
 [import, lang:"v"](code/v/jarvis.v)
 {% sample lang="rust" %}
 [import, lang:"rust"](code/rust/jarvis_march.rs)
+{% sample lang="scala" %}
+[import, lang:"scala"](code/scala/jarvisMarch.scala)
 {% endmethod %}
 
 <script>