The challenge
Given a set of numbers, return the additive inverse of each. Each positive becomes negatives, and the negatives become positives.
invert([1,2,3,4,5]) == [-1,-2,-3,-4,-5]
invert([1,-2,3,-4,5]) == [-1,2,-3,4,-5]
invert([]) == []
The solution in Kotlin code
Option 1:
fun invert(arr: IntArray) = arr.map { -it }.toIntArray()
Option 2:
fun invert(arr: IntArray): IntArray {
return IntArray(arr.size){ -arr[it] }
}
Option 3:
fun invert(arr: IntArray): IntArray {
var x = 0
while (x < arr.size) {
arr[x] = arr[x] * -1
x++
}
return arr
}
Test cases to validate our solution
import org.junit.Assert.*;
import org.junit.Test
class TestExample {
@Test
fun testFixed() {
assertArrayEquals(intArrayOf(-1,-2,-3,-4,-5), invert(intArrayOf(1,2,3,4,5)))
assertArrayEquals(intArrayOf(-1,2,-3,4,-5), invert(intArrayOf(1,-2,3,-4,5)))
assertArrayEquals(intArrayOf(), invert(intArrayOf()))
assertArrayEquals(intArrayOf(0), invert(intArrayOf(0)))
}
}
