Better way of converting a Map[K, Option[V]] to a Map[K,V]

Question

I have some code that is producing a Map where the values are Option types, and I really of course want a map containing only the real values.

Answer 1

for ((k, Some(v)) <- input) yield (k, v)

It's franza's answer from a later question, but it deserves a re-post here.

Answer 2

input flatMap {case(k,ov) => ov map {v => (k, v)}}

Answer 3

input.collect{case (k, Some(v)) => (k,v)}