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SergiiVlasiuk's solution

to Minesweeper in the Scala Track

Published at Aug 26 2019 · 0 comments
Instructions
Test suite
Solution

Add the numbers to a minesweeper board.

Minesweeper is a popular game where the user has to find the mines using numeric hints that indicate how many mines are directly adjacent (horizontally, vertically, diagonally) to a square.

In this exercise you have to create some code that counts the number of mines adjacent to a square and transforms boards like this (where * indicates a mine):

+-----+
| * * |
|  *  |
|  *  |
|     |
+-----+

into this:

+-----+
|1*3*1|
|13*31|
| 2*2 |
| 111 |
+-----+

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.

Submitting Incomplete Solutions

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

MinesweeperTest.scala

import org.scalatest.{Matchers, FunSuite}

/** @version 1.1.0 */
class MinesweeperTest extends FunSuite with Matchers {

  test("no rows") {
    Minesweeper.annotate(List()) should be(List())
  }

  test("no columns") {
    pending
    Minesweeper.annotate(List("")) should be(List(""))
  }

  test("no mines") {
    pending
    Minesweeper.annotate(List("   ",
                              "   ",
                              "   ")) should be(
      List("   ",
           "   ",
           "   "))
  }

  test("minefield with only mines") {
    pending
    Minesweeper.annotate(List("***",
                              "***",
                              "***")) should be(
      List("***",
           "***",
           "***"))
  }

  test("mine surrounded by spaces") {
    pending
    Minesweeper.annotate(List("   ",
                              " * ",
                              "   ")) should be(
      List("111",
           "1*1",
           "111"))
  }

  test("space surrounded by mines") {
    pending
    Minesweeper.annotate(List("***",
                              "* *",
                              "***")) should be(
      List("***",
           "*8*",
           "***"))
  }

  test("horizontal line") {
    pending
    Minesweeper.annotate(List(" * * ")) should be(List("1*2*1"))
  }

  test("horizontal line, mines at edges") {
    pending
    Minesweeper.annotate(List("*   *")) should be(List("*1 1*"))
  }

  test("vertical line") {
    pending
    Minesweeper.annotate(List(" ",
                              "*",
                              " ",
                              "*",
                              " ")) should be(
      List("1",
           "*",
           "2",
           "*",
           "1"))
  }

  test("vertical line, mines at edges") {
    pending
    Minesweeper.annotate(List("*",
                              " ",
                              " ",
                              " ",
                              "*")) should be(
      List("*",
           "1",
           " ",
           "1",
           "*"))
  }

  test("cross") {
    pending
    Minesweeper.annotate(List("  *  ",
                              "  *  ",
                              "*****",
                              "  *  ",
                              "  *  ")) should be(
      List(" 2*2 ",
           "25*52",
           "*****",
           "25*52",
           " 2*2 "))
  }

  test("large minefield") {
    pending
    Minesweeper.annotate(List(" *  * ",
                              "  *   ",
                              "    * ",
                              "   * *",
                              " *  * ",
                              "      ")) should be(
      List("1*22*1",
           "12*322",
           " 123*2",
           "112*4*",
           "1*22*2",
           "111111"))
  }
}
object Minesweeper {
  def annotate(list: List[String]): List[String] = {
    if (list.isEmpty) return list
    val matrix = list.map(_.toList)
    matrix.indices.map(i => matrix(i).indices.map(j => calcCells(i, j, matrix)).mkString).toList
  }

  private def calcCells(x: Int, y: Int, matrix: List[List[Char]]): String = {
    if (matrix(x)(y) == '*') return "*"
    val s = (
      for {i <- x - 1 to x + 1
           if i >= 0 && i < matrix.length
           j <- y - 1 to y + 1
           if j >= 0 && j < matrix.head.length
      } yield if (matrix(i)(j) == '*') 1 else 0).sum
    if (s == 0) " "
    else s.toString
  }
}

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