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SergiiVlasiuk's solution

to Word Count in the Scala Track

Published at Aug 18 2019 · 0 comments
Test suite

Given a phrase, count the occurrences of each word in that phrase.

For example for the input "olly olly in come free"

olly: 2
in: 1
come: 1
free: 1

The Scala exercises assume an SBT project scheme. The exercise solution source should be placed within the exercise directory/src/main/scala. The exercise unit tests can be found within the exercise directory/src/test/scala.

To run the tests simply run the command sbt test in the exercise directory.

For more detailed info about the Scala track see the help page.


This is a classic toy problem, but we were reminded of it by seeing it in the Go Tour.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


import org.scalatest.{Matchers, FunSuite}

/** @version 1.2.0 */
class WordCountTest extends FunSuite with Matchers {

  test("count one word") {
    WordCount("word").countWords should be(Map(("word", 1)))

  test("count one of each word") {
    WordCount("one of each").countWords should be(
      Map(("one", 1), ("of", 1), ("each", 1)))

  test("multiple occurrences of a word") {
    WordCount("one fish two fish red fish blue fish").countWords should be(
      Map(("blue", 1), ("two", 1), ("fish", 4), ("one", 1), ("red", 1)))

  test("handles cramped lists") {
    WordCount("one,two,three").countWords should be(
      Map(("one", 1), ("two", 1), ("three", 1)))

  test("handles expanded lists") {
    WordCount("one,\ntwo,\nthree").countWords should be(
      Map(("one", 1), ("two", 1), ("three", 1)))

  test("ignore punctuation") {
    WordCount("car: carpet as java: javascript!!&@$%^&").countWords should be(
      Map(("as", 1), ("car", 1), ("java", 1), ("carpet", 1), ("javascript", 1)))

  test("include numbers") {
    WordCount("testing, 1, 2 testing").countWords should be(
      Map(("testing", 2), ("1", 1), ("2", 1)))

  test("normalize case") {
    WordCount("go Go GO Stop stop").countWords should be(
      Map(("go", 3), ("stop", 2)))

  test("with apostrophes") {
    WordCount("First: don\'t laugh. Then: don\'t cry.").countWords should be(
      Map(("laugh", 1), ("don't", 2), ("then", 1), ("first", 1), ("cry", 1)))

  test("with quotations") {
    WordCount("Joe can\'t tell between \'large\' and large.").countWords should be(
      Map(("can't", 1),
          ("large", 2),
          ("joe", 1),
          ("between", 1),
          ("tell", 1),
          ("and", 1)))

  test("multiple spaces not detected as a word") {
    WordCount(" multiple   whitespaces").countWords should be(
      Map(("multiple", 1), ("whitespaces", 1)))
case class WordCount(words: String) {
  //  def countWords: Map[String, Int] = ("[^\\w']+".r).split(words)
  def countWords: Map[String, Int] = words.split("[^\\w']+")
    .map(_.replaceAll("^\'|\'$", ""))
    .mapValues(x => x.size)

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