2016 Update

Task/Knapsack-problem-Unbounded/Scala/knapsack-problem-unbounded.scala

@@ -0,0 +1,42 @@
+import scala.annotation.tailrec
+
+case class Item(name: String, value: Int, weight: Double, volume: Double)
+
+val items = List(
+  Item("panacea", 3000, 0.3, 0.025),
+  Item("ichor", 1800, 0.2, 0.015),
+  Item("gold", 2500, 2.0, 0.002))
+
+val (maxWeight, maxVolume) = (25, 0.25)
+
+def show(is: List[Item]) =
+  (items.map(_.name) zip items.map(i => is.count(_ == i))).map {
+    case (i, c) => s"$i: $c"
+  }.mkString(", ")
+
+case class Knapsack(items: List[Item]) {
+  def value = items.foldLeft(0)(_ + _.value)
+  def weight = items.foldLeft(0.0)(_ + _.weight)
+  def volume = items.foldLeft(0.0)(_ + _.volume)
+  def isFull = !((weight <= maxWeight) && (volume <= maxVolume))
+  override def toString =
+    s"[${show(items)} | value: $value, weight: $weight, volume: $volume]"
+}
+
+def fill(knapsack: Knapsack): List[Knapsack] =
+  items.map(i => Knapsack(i :: knapsack.items))
+
+//cause brute force
+def distinct(list: List[Knapsack]) =
+  list.map(k => Knapsack(k.items.sortBy(_.name))).distinct
+
+@tailrec
+def f(notPacked: List[Knapsack], packed: List[Knapsack]): List[Knapsack] =
+  notPacked match {
+    case Nil => packed.sortBy(_.value).takeRight(4)
+    case _ =>
+      val notFull = distinct(notPacked.flatMap(fill)).filterNot(_.isFull)
+      f(notFull, notPacked ::: packed)
+  }
+
+f(items.map(i => Knapsack(List(i))), Nil).foreach(println)