Compare 2 different strings and finding matching letters and count of matched

// Here we are going to compare 2 different strings and finding matching letters and count of matched

 val firstString = "uuai aao ioaau eieoiou"
 val secondString = "i love india and singapore"
 val m = new Array[Char](50)
 var i = 0
 var leftString  = ""


 for (c <- firstString) {
     m(i) = c
     i = i  + 1
     }

  for (c <- m.distinct.sorted(Ordering.Char)){
                if (c != null) {
      leftString = leftString + c.toString
      }
      }

  m.distinct.sorted(Ordering.Char)

  var output = Map[String,String]()
  var count = 0
  for (lc <- leftString) {
     count =   secondString.count(_ == lc)
     output = output + (lc.toString ->count.toString)
     }

 println(output)

 scala>  println(output)
Map(e -> 2,  -> 0, u -> 0, a -> 3, i -> 4,   -> 4, o -> 2)