title: Scala recursion solving a sudoku
body: <p>I need to write a method that will return the contents of a particular row (index of it is inputted as method parameter). I do not have a huge experience in Scala and therefore I am getting confused. I would do something like a for loop for 1 to 9 if row is not empty return value, however, I have to use recursion and no loops and I am also given this method definitions : </p>
  
  <pre><code>   def r(r: Int): Set[Int] = {
    //code
     }
  </code></pre>
  
  <p>I also do not know how Set works. Any help would be really appreciated. PS: I am not asking for complete code, an algorithm explanation would be more than enough!</p>