Family Day update

Task/Sorting-algorithms-Merge-sort/Scala/sorting-algorithms-merge-sort.scala

@@ -0,0 +1,21 @@
+object MergeSort extends App {
+
+  def mergeSort(input: List[Int]): List[Int] = {
+    def merge(left: List[Int], right: List[Int]): LazyList[Int] = (left, right) match {
+      case (x :: xs, y :: ys) if x <= y => x #:: merge(xs, right)
+      case (x :: xs, y :: ys) => y #:: merge(left, ys)
+      case _ => if (left.isEmpty) right.to(LazyList) else left.to(LazyList)
+    }
+
+    def sort(input: List[Int], length: Int): List[Int] = input match {
+      case Nil | List(_) => input
+      case _ =>
+        val middle = length / 2
+        val (left, right) = input splitAt middle
+        merge(sort(left, middle), sort(right, middle + length % 2)).toList
+    }
+
+    sort(input, input.length)
+  }
+
+}