Heap Sort Algorithm in Kotlin

import java.util.*

fun <E: Comparable<E>> Array<E>.sort() {
    val middle = size / 2 - 1
    for (i in middle downTo 0) {
        heapify(this, size, i)
    }
    for (i in size - 1 downTo 0) {
        this[0] = this[i].also { this[i] = this[0] }
        heapify(this, i, 0)
    }
}

private fun <E: Comparable<E>> heapify(arr: Array<E>, heapSize: Int, root: Int) {
    var largest = root
    val leftNode = 2 * root + 1
    val rightNode = 2 * root + 2
    if (leftNode < heapSize && arr[leftNode] > arr[largest]) largest = leftNode
    if (rightNode < heapSize && arr[rightNode] > arr[largest]) largest = rightNode

    if (largest != root) {
        arr[root] = arr[largest].also { arr[largest] = arr[root] }
        heapify(arr, heapSize, largest)
    }
}

fun main(args: Array<String>) {
    val nums = arrayOf(2, 12, 89, 23, 76, 43, 12)
    nums.sort()
    println(Arrays.toString(nums))

    val languages = arrayOf("Kotlin", "Java", "C#", "R", "Python", "Scala", "Groovy", "C", "C++")
    languages.sort()
    println(Arrays.toString(languages))
}

Output:

[2, 12, 12, 23, 43, 76, 89]
[C, C#, C++, Groovy, Java, Kotlin, Python, R, Scala]