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SergiiVlasiuk's solution

to High Scores in the Scala Track

Published at Aug 23 2019 · 0 comments
Instructions
Test suite
Solution

Manage a game player's High Score list.

Your task is to build a high-score component of the classic Frogger game, one of the highest selling and addictive games of all time, and a classic of the arcade era. Your task is to write methods that return the highest score from the list, the last added score, the three highest scores, and a report on the difference between the last and the highest scores.

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

Tribute to the eighties' arcade game Frogger

Submitting Incomplete Solutions

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

HighScoresTest.scala

import org.scalatest.{Matchers, FunSuite}

/** @version 2.0.0 */
class HighScoresTest extends FunSuite with Matchers {

  test("Latest score") {
    HighScores.latest(List(100, 0, 90, 30)) should be(30)
  }

  test("Personal best") {
    pending
    HighScores.personalBest(List(40, 100, 70)) should be(100)
  }

  test("Personal top") {
    pending
    HighScores.personalTop(List(50, 30, 10)) should be(List(50, 30, 10))
  }

  test("Personal top highest to lowest") {
    pending
    HighScores.personalTop(List(20, 10, 30)) should be(List(30, 20, 10))
  }

  test("Personal top when there is a tie") {
    pending
    HighScores.personalTop(List(40, 20, 40, 30)) should be(List(40, 40, 30))
  }

  test("Personal top when there are less than 3") {
    pending
    HighScores.personalTop(List(30, 70)) should be(List(70, 30))
  }

  test("Personal top when there is only one") {
    pending
    HighScores.personalTop(List(40)) should be(List(40))
  }

  test("Personal top from a long list") {
    pending
    HighScores.personalTop(
      List(10, 30, 90, 30, 100, 20, 10, 0, 30, 40, 40, 70, 70)) should be(
      List(100, 90, 70))
  }

  test("Message for new personal best") {
    pending
    HighScores.report(List(20, 40, 0, 30, 70)) should be(
      "Your latest score was 70. That's your personal best!")
  }

  test("Message when latest score is not the highest score") {
    pending
    HighScores.report(List(20, 100, 0, 30, 70)) should be(
      "Your latest score was 70. That's 30 short of your personal best!")
  }

  test("Message for repeated personal best") {
    pending
    HighScores.report(List(20, 70, 50, 70, 30)) should be(
      "Your latest score was 30. That's 40 short of your personal best!")
  }
}
object HighScores {
  def personalTop(scores: List[Int]): List[Int] = scores.sortBy(-_) take 3

  def personalBest(scores: List[Int]): Int = scores.max

  def latest(scores: List[Int]): Int = scores.last

  def report(scores: List[Int]): String = {
    val latestScore: Int = latest(scores)
    val best = personalBest(scores)
    val diff = if(best <= latestScore) ""
    else  best - latestScore + " short of "
    s"Your latest score was ${latestScore}. That's ${diff}your personal best!"
  }
}

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