Quick coding test. Given tasks to people, find person with most tasks, that finished first

FirstToFinishMost.scala

 // Broken apart to ease understanding.
val s1=Seq(1,1,1,2,2,2,3,3,3,3,4,4,4,4,1)         

val groups=s1.groupBy { identity }                

val sizes=groups.mapValues { _.size}          
val maxSize=sizes.values.max                  
val maxUsers=sizes.filter(_._2==maxSize).keys.toSet
val pop=s1.filter(maxUsers).zipWithIndex
val lastPlaces=pop.groupBy(_._1).mapValues(_.last)
val quickest=lastPlaces.values.minBy(_._2)._1