Count of unique characters in string

Question

I need to write a function that returns a List of (Char, Int) pairs given an input String.

My solution produces the correct result but I'm wondering if there is a better way:

def countChars(s: String): List[(Char, Int)] = {
    s.groupBy(c => c.toLower).flatMap(e => List((e._1, e._2.length))).toList
  }                                              

This produces a result like this in a worksheet:

countChars("Green Grass")
// res0: List[(Char, Int)] = List(('e', 2), ('s', 2), ('n', 1), ('a', 1), (' ', 1), ('g', 2), ('r', 2))

Answer 1

Making a singleton List just to flatten it is redundant.

"Green Grass".groupBy(c => c.toLower).map(e => (e._1, e._2.length)).toList