Exercise: Best students list

Implement makeBestStudentsList function to display the best 10 students, so they can get an internship. You should compare them by their result (higher is better). To get an internship, students need to have got at least 30 points in the semester and a result of at least 80. The best student gets 5000 USD, the next 3 get 3000 USD and the next 6 get 1000 USD. Display them in a single string, presenting each student in a new line, in alphabetical order (sorting by surname, and for equals surnames by name), in the format “{name} {surname}, ${internship size}”. Starting code:

fun List<Student>.makeBestStudentsList(): String = TODO()

data class Student(
    val name: String,
    val surname: String,
    val result: Double,
    val pointsInSemester: Int
)

This problem can either be solved in the below playground or you can clone kotlin-exercises project and solve it locally. In the project, you can find code template for this exercise in functional/collections/BestStudents.kt. You can find there starting code and unit tests.

Once you are done with the exercise, you can check your solution here.

Playground

import org.junit.Test
import kotlin.test.assertEquals

fun List<Student>.makeBestStudentsList(): String = TODO()

data class Student(
    val name: String,
    val surname: String,
    val result: Double,
    val pointsInSemester: Int
)

class BestStudentsListTest {
    val internshipStudent = Student("Marc", "Smith", 87.0, 32)
    val studentWithTooLowResultToInternship = Student("Marcus", "Smith", 37.0, 32)
    val studentWithNotEnoughPointsForInternship = Student("Marcello", "Smith", 87.0, 12)
    val studentNotPassingBecauseOfResult = Student("Peter", "Jackson", 21.0, 24)
    val studentNotPassingBecauseOfPoints = Student("Michael", "Angelo", 71.0, 12)

    val allStudents = listOf(
            internshipStudent,
            studentWithTooLowResultToInternship,
            studentWithNotEnoughPointsForInternship,
            studentNotPassingBecauseOfResult,
            Student("Noely", "Peterson", 91.0, 22),
            studentNotPassingBecauseOfPoints,
            Student("Noe", "Samson", 41.0, 18),
            Student("Timothy", "Johnson", 51.0, 15),
            Student("Noe", "Peterson", 91.0, 22),
            Student("Ester", "Adams", 81.0, 30),
            Student("Dior", "Angel", 88.5, 38),
            Student("Naja", "Marcson", 100.0, 31),
            Student("Oregon", "Dart", 85.5, 30),
            Student("Ron", "Peters", 89.0, 31),
            Student("Harry", "Potter", 80.0, 30),
            Student("Sansa", "Stark", 49.5, 14),
            Student("Jamme", "Lannister", 80.0, 30),
            Student("Alex", "Nolan", 86.0, 33),
            Student("Jon", "Johnson", 85.1, 31),
            Student("James", "Johnson", 85.2, 31),
            Student("Jack", "Johnson", 85.3, 31)
    )

    @Test
    fun `Single student that matches criteria gets biggest internship`() {
        val text = listOf(internshipStudent).makeBestStudentsList()
        val expected = "Marc Smith, \$5000"
        assertEquals(expected, text)
    }

    @Test
    fun `Single student with too low result doesn't get internship`() {
        val text = listOf(studentWithTooLowResultToInternship).makeBestStudentsList()
        assertEquals("", text)
    }

    @Test
    fun `Result 80 is acceptable`() {
        val student = Student("Noely", "Peterson", 80.0, 32)
        val text = listOf(student).makeBestStudentsList()
        assertEquals("Noely Peterson, \$5000", text)
    }

    @Test
    fun `30 points is acceptable`() {
        val student = Student("Noely", "Peterson", 81.0, 30)
        val text = listOf(student).makeBestStudentsList()
        assertEquals("Noely Peterson, \$5000", text)
    }

    @Test
    fun `Single student with not enough doesn't get internship`() {
        val text = listOf(studentWithNotEnoughPointsForInternship).makeBestStudentsList()
        assertEquals("", text)
    }

    @Test
    fun `Complex test`() {
        val text = allStudents.makeBestStudentsList()
        val expected = """
            Ester Adams, ${'$'}1000
            Dior Angel, ${'$'}3000
            Oregon Dart, ${'$'}1000
            Jack Johnson, ${'$'}1000
            James Johnson, ${'$'}1000
            Jon Johnson, ${'$'}1000
            Naja Marcson, ${'$'}5000
            Alex Nolan, ${'$'}1000
            Ron Peters, ${'$'}3000
            Marc Smith, ${'$'}3000
        """.trimIndent()
        assertEquals(expected, text)
    }
}