 # chisun-joung's solution

## to Sum Of Multiples in the Kotlin Track

Published at Oct 21 2019 · 0 comments
Instructions
Test suite
Solution

Given a number, find the sum of all the unique multiples of particular numbers up to but not including that number.

If we list all the natural numbers below 20 that are multiples of 3 or 5, we get 3, 5, 6, 9, 10, 12, 15, and 18.

The sum of these multiples is 78.

## 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 variation on Problem 1 at Project Euler http://projecteuler.net/problem=1

## Submitting Incomplete Solutions

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

### SumOfMultiplesTest.kt

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

class SumOfMultiplesTest {

@Test
fun `multiples of 3 or 5 up to 1`() {
assertEquals(0, SumOfMultiples.sum(setOf(3, 5), 1))
}

@Test
@Ignore
fun `multiples of 3 or 5 up to 4`() {
assertEquals(3, SumOfMultiples.sum(setOf(3, 5), 4))
}

@Test
@Ignore
fun `multiples of 3 up to 7`() {
assertEquals(9, SumOfMultiples.sum(setOf(3), 7))
}

@Test
@Ignore
fun `multiples of 3 or 5 up to 10`() {
assertEquals(23, SumOfMultiples.sum(setOf(3, 5), 10))
}

@Test
@Ignore
fun `multiples of 3 or 5 up to 100`() {
assertEquals(2318, SumOfMultiples.sum(setOf(3, 5), 100))
}

@Test
@Ignore
fun `multiples of 3 or 5 up to 1000`() {
assertEquals(233168, SumOfMultiples.sum(setOf(3, 5), 1000))
}

@Test
@Ignore
fun `multiples of 7, 13 or 17 up to 20`() {
assertEquals(51, SumOfMultiples.sum(setOf(7, 13, 17), 20))
}

@Test
@Ignore
fun `multiples of 4 or 6 up to 15`() {
assertEquals(30, SumOfMultiples.sum(setOf(4, 6), 15))
}

@Test
@Ignore
fun `multiples of 5, 6 or 8 up to 150`() {
assertEquals(4419, SumOfMultiples.sum(setOf(5, 6, 8), 150))
}

@Test
@Ignore
fun `multiples of 5 or 25 up to 51`() {
assertEquals(275, SumOfMultiples.sum(setOf(5, 25), 51))
}

@Test
@Ignore
fun `multiples of 43 or 47 up to 10000`() {
assertEquals(2203160, SumOfMultiples.sum(setOf(43, 47), 10000))
}

@Test
@Ignore
fun `multiples of 1 up to 100`() {
assertEquals(4950, SumOfMultiples.sum(setOf(1), 100))
}

@Test
@Ignore
fun `multiples of an empty set up to 10000`() {
assertEquals(0, SumOfMultiples.sum(emptySet(), 10000))
}

}``````
``````class SumOfMultiples {
companion object{
fun sum(multiples: Set<Int>, limitNum: Int): Int = multiples
.flatMap { (0 until limitNum).step(it) }
.toSet()
.sum()
}
}``````