Add Intersection Correct example from lecture 3

src/main/scala/lecture3/03_IntersectionWrong.scala

@@ -5,14 +5,14 @@ import scala.collection.parallel.CollectionConverters.IterableIsParallelizable
 import org.scalameter._
 
 // TODO : THIS DOES NOT COMPILE
-def intersection(a: GenSet[Int], b: GenSet[Int]): Set[Int] =
+def intersection_wrong(a: GenSet[Int], b: GenSet[Int]): Set[Int] =
   val result = mutable.Set[Int]()
   for (x <- a) if (b contains x) result += x
   result
 
 @main def intersectionWrong =
-  val seqres = intersection((0 until 1000).toSet, (0 until 1000 by 4).toSet)
-  val parres = intersection((0 until 1000).par.toSet, (0 until 1000 by 4).par.toSet)
+  val seqres = intersection_wrong((0 until 1000).toSet, (0 until 1000 by 4).toSet)
+  val parres = intersection_wrong((0 until 1000).par.toSet, (0 until 1000 by 4).par.toSet)
   log(s"Sequential result - ${seqres.size}")
   log(s"Parallel result - ${parres.size}")
 

src/main/scala/lecture3/04_IntersectionCorrect.scala

+package lecture3
+
+import org.scalameter.*
+
+import java.util.*
+import java.util.concurrent.ConcurrentSkipListSet
+import scala.collection.*
+import scala.collection.parallel.CollectionConverters.IterableIsParallelizable
+
+// TODO : THIS DOES NOT COMPILE
+def intersection_correct(a: GenSet[Int], b: GenSet[Int]) =
+  val result = new ConcurrentSkipListSet[Int]()
+  for (x <- a) if (b contains x) result add x
+  result
+
+@main def intersectionCorrect =
+  val seqres = intersection_correct((0 until 1000).toSet, (0 until 1000 by 4).toSet)
+  val parres = intersection_correct((0 until 1000).par.toSet, (0 until 1000 by 4).par.toSet)
+  log(s"Sequential result - ${seqres.size}")
+  log(s"Parallel result - ${parres.size}")
+
+