Data commit

Task/Hash-join/Scala/hash-join.scala

@@ -0,0 +1,19 @@
+def join[Type](left: Seq[Seq[Type]], right: Seq[Seq[Type]]) = {
+    val hash = right.groupBy(_.head) withDefaultValue Seq()
+    left.flatMap(cols => hash(cols.last).map(cols ++ _.tail))
+}
+
+// Example:
+
+val table1 = List(List("27", "Jonah"),
+                  List("18", "Alan"),
+                  List("28", "Glory"),
+                  List("18", "Popeye"),
+                  List("28", "Alan"))
+val table2 = List(List("Jonah", "Whales"),
+                  List("Jonah", "Spiders"),
+                  List("Alan", "Ghosts"),
+                  List("Alan", "Zombies"),
+                  List("Glory", "Buffy"))
+
+println(join(table1, table2) mkString "\n")