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ajablonski's solution

to Raindrops in the Scala Track

Published at Oct 05 2019 · 0 comments
Instructions
Test suite
Solution

Convert a number to a string, the contents of which depend on the number's factors.

  • If the number has 3 as a factor, output 'Pling'.
  • If the number has 5 as a factor, output 'Plang'.
  • If the number has 7 as a factor, output 'Plong'.
  • If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.

Examples

  • 28's factors are 1, 2, 4, 7, 14, 28.
    • In raindrop-speak, this would be a simple "Plong".
  • 30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
    • In raindrop-speak, this would be a "PlingPlang".
  • 34 has four factors: 1, 2, 17, and 34.
    • In raindrop-speak, this would be "34".

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.

Source

A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

Submitting Incomplete Solutions

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

RaindropsTest.scala

import org.scalatest.{Matchers, FunSuite}

/** @version 1.1.0 */
class RaindropsTest extends FunSuite with Matchers {
  
  test("the sound for 1 is 1") {
    Raindrops.convert(1) should be ("1")
  }

  test("the sound for 3 is Pling") {
    pending
    Raindrops.convert(3) should be ("Pling")
  }

  test("the sound for 5 is Plang") {
    pending
    Raindrops.convert(5) should be ("Plang")
  }

  test("the sound for 7 is Plong") {
    pending
    Raindrops.convert(7) should be ("Plong")
  }

  test("the sound for 6 is Pling as it has a factor 3") {
    pending
    Raindrops.convert(6) should be ("Pling")
  }

  test("2 to the power 3 does not make a raindrop sound as 3 is the exponent not the base") {
    pending
    Raindrops.convert(8) should be ("8")
  }

  test("the sound for 9 is Pling as it has a factor 3") {
    pending
    Raindrops.convert(9) should be ("Pling")
  }

  test("the sound for 10 is Plang as it has a factor 5") {
    pending
    Raindrops.convert(10) should be ("Plang")
  }

  test("the sound for 14 is Plong as it has a factor of 7") {
    pending
    Raindrops.convert(14) should be ("Plong")
  }

  test("the sound for 15 is PlingPlang as it has factors 3 and 5") {
    pending
    Raindrops.convert(15) should be ("PlingPlang")
  }

  test("the sound for 21 is PlingPlong as it has factors 3 and 7") {
    pending
    Raindrops.convert(21) should be ("PlingPlong")
  }

  test("the sound for 25 is Plang as it has a factor 5") {
    pending
    Raindrops.convert(25) should be ("Plang")
  }

  test("the sound for 27 is Pling as it has a factor 3") {
    pending
    Raindrops.convert(27) should be ("Pling")
  }

  test("the sound for 35 is PlangPlong as it has factors 5 and 7") {
    pending
    Raindrops.convert(35) should be ("PlangPlong")
  }

  test("the sound for 49 is Plong as it has a factor 7") {
    pending
    Raindrops.convert(49) should be ("Plong")
  }

  test("the sound for 52 is 52") {
    pending
    Raindrops.convert(52) should be ("52")
  }

  test("the sound for 105 is PlingPlangPlong as it has factors 3, 5 and 7") {
    pending
    Raindrops.convert(105) should be ("PlingPlangPlong")
  }

  test("the sound for 3125 is Plang as it has a factor 5") {
    pending
    Raindrops.convert(3125) should be ("Plang")
  }
}
object Raindrops {
  private case class FactorAndWord(factor: Int, word: String)

  private val words = Seq(
    FactorAndWord(3, "Pling"),
    FactorAndWord(5, "Plang"),
    FactorAndWord(7, "Plong")
  )

  def convert(n: Int): String = {
    words
      .flatMap(word => if (n % word.factor == 0) Some(word.word) else None)
      .reduceOption(_ + _)
      .getOrElse(n.toString)
  }
}

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