[Scala-Way] Add greedy package and min refuel problem

Author: ashwinbhaskar

scala-way/src/main/scala/greedy/MinimumRefuels.scala

@@ -0,0 +1,26 @@
+package greedy
+
+/*
+Find the minimum stops for refueling required by a car on it's journey from point A to point B
+*/
+
+object MinimumRefuels extends App{
+    /*
+        stops: Array of distances at which fuel stations are present from point A
+        distanceToPointB: Distance to point B from current station
+        maxDistanceOnFullTank: The max distance the car can cover when it's tank is full
+    */
+
+    def minimumRefuels(stops: Array[Int], distanceToPointB: Int)(implicit maxDistanceOnFullTank: Int): Option[Int] = stops match {
+        case Array(stop1, _ *) if stop1 > maxDistanceOnFullTank => None
+        case _ => stops.indices.find(index => stops(index) >= maxDistanceOnFullTank) match {
+            case Some(stopIndex) => 
+                val greedyHopIndex = if(stops(stopIndex) == maxDistanceOnFullTank) stopIndex else stopIndex - 1
+                val distanceCovered = stops(greedyHopIndex)
+                val updatedStops = stops.drop(stopIndex).map(_ - distanceCovered)
+                minimumRefuels(updatedStops, distanceToPointB - distanceCovered).map(_ + 1)
+            case None => Some(0)
+        }
+    }
+}
+

scala-way/src/test/scala/MinRefuelsTest.scala

@@ -0,0 +1,24 @@
+import org.scalatest.FunSuite
+import greedy.MinimumRefuels
+
+class MinRefuelsTest extends FunSuite {
+
+    test("Should return the correct min refuels when solution is possible"){
+        val stops = Array(10,40,70,80)
+        val minRefuels = MinimumRefuels.minimumRefuels(stops = stops, distanceToPointB = 100)(maxDistanceOnFullTank = 30)
+        assert(minRefuels == Some(3))
+    }
+
+    test("Should return none if there solution is not possible"){
+        val stops = Array(10,50,70,80)
+        val minRefuels = MinimumRefuels.minimumRefuels(stops = stops, distanceToPointB = 100)(maxDistanceOnFullTank = 30)
+        assert(minRefuels == None)
+    }
+
+    test("Should return 0 when no stops are required"){
+        val stops = Array(10,50,70,80)
+        val minRefuels = MinimumRefuels.minimumRefuels(stops = stops, distanceToPointB = 100)(maxDistanceOnFullTank = 101)
+        assert(minRefuels == Some(0))
+    }
+
+}