I'm trying to reduce the extent to which I write Scala (2.8) like Java. Here's a simplification of a problem I came across. Can you suggest improvements on my solutions that are "more functional"?

Transform the map

val inputMap = mutable.LinkedHashMap(1->'a',2->'a',3->'b',4->'z',5->'c')

by discarding any entries with value 'z' and indexing the characters as they are encountered

First try

var outputMap = new mutable.HashMap[Char,Int]()
var counter = 0
for(kvp <- inputMap){
  val character = kvp._2
  if(character !='z' && !outputMap.contains(character)){
    outputMap += (character -> counter)
    counter += 1
  }
}

Second try (not much better, but uses an immutable map and a 'foreach')

var outputMap = new immutable.HashMap[Char,Int]()
var counter = 0
inputMap.foreach{
  case(number,character) => {
    if(character !='z' && !outputMap.contains(character)){
      outputMap2 += (character -> counter)
      counter += 1
    }
  }
}