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anwarsky's solution

to Grade School in the Kotlin Track

Published at Sep 07 2019 · 0 comments
Instructions
Test suite
Solution

Given students' names along with the grade that they are in, create a roster for the school.

In the end, you should be able to:

  • Add a student's name to the roster for a grade
    • "Add Jim to grade 2."
    • "OK."
  • Get a list of all students enrolled in a grade
    • "Which students are in grade 2?"
    • "We've only got Jim just now."
  • Get a sorted list of all students in all grades. Grades should sort as 1, 2, 3, etc., and students within a grade should be sorted alphabetically by name.
    • "Who all is enrolled in school right now?"
    • "Grade 1: Anna, Barb, and Charlie. Grade 2: Alex, Peter, and Zoe. Grade 3…"

Note that all our students only have one name. (It's a small town, what do you want?)

For bonus points

Did you get the tests passing and the code clean? If you want to, these are some additional things you could try:

  • If you're working in a language with mutable data structures and your implementation allows outside code to mutate the school's internal DB directly, see if you can prevent this. Feel free to introduce additional tests.

Then please share your thoughts in a comment on the submission. Did this experiment make the code better? Worse? Did you learn anything from it?

Setup

Go through the setup instructions for Kotlin to install the necessary dependencies:

https://exercism.io/tracks/kotlin/installation

Making the test suite pass

Execute the tests with:

$ gradlew test

Use gradlew.bat if you're on Windows

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the @Ignore annotation.

Source

A pairing session with Phil Battos at gSchool http://gschool.it

Submitting Incomplete Solutions

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

SchoolTest.kt

import org.junit.Before
import org.junit.Test
import org.junit.Ignore
import kotlin.test.assertEquals
import kotlin.test.assertTrue

class SchoolTest {

    private lateinit var school: School

    @Before
    fun beforeTest() {
        school = School()
    }


    @Test
    fun startsWithNoStudents() {
        assertTrue(school.db().isEmpty())
    }

    @Ignore
    @Test
    fun addsStudents() {
        school.add("Aimee", 2)

        val expected = mapOf(2 to listOf("Aimee"))
        assertEquals(expected, school.db())
    }

    @Ignore
    @Test
    fun addsMoreStudentsInSameGrade() {
        val grade = 2
        school.add("James", grade)
        school.add("Blair", grade)
        school.add("Paul", grade)

        val expected = mapOf(2 to listOf("James", "Blair", "Paul"))
        assertEquals(expected, school.db())
    }

    @Ignore
    @Test
    fun addsStudentsInMultipleGrades() {
        school.add("Chelsea", 3)
        school.add("Logan", 7)

        val expected = mapOf(3 to listOf("Chelsea"), 7 to listOf("Logan"))
        assertEquals(expected, school.db())
    }

    @Ignore
    @Test
    fun getsStudentsInAGrade() {
        school.add("Franklin", 5)
        school.add("Bradley", 5)
        school.add("Jeff", 1)

        val expected = mapOf(5 to listOf("Franklin", "Bradley"), 1 to listOf("Jeff"))
        assertEquals(expected, school.db())
    }

    @Ignore
    @Test
    fun getsStudentsInEmptyGrade() {
        assertTrue(school.grade(1).isEmpty())
    }

    @Ignore
    @Test
    fun sortsSchool() {
        school.add("Jennifer", 4)
        school.add("Kareem", 6)
        school.add("Christopher", 4)
        school.add("Kyle", 3)

        val expected = mapOf(3 to listOf("Kyle"), 4 to listOf("Christopher", "Jennifer"), 6 to listOf("Kareem"))
        val sortedClasses = school.sort()
        assertEquals(listOf(3, 4, 6), sortedClasses.keys.toList(), "Grades not sorted in ascending order")
        assertEquals(expected, sortedClasses)

    }
}
class School(val db: MutableMap<Int, MutableList<String>> = mutableMapOf()) {
    fun add(name: String, grade: Int) =  (db.getOrPut(grade) { mutableListOf()}).add(name)
    fun grade(g: Int) = db.getOrDefault(g, MutableList(0) {i -> ""})
    fun db() = db
    fun sort(): Map<Int, List<String>> = (db.toSortedMap().map { e -> e.key to e.value.sorted() }).toMap()

}

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