Merge sort in Kotlin

mergesort.kt

sortArray(intArrayOf(5, 2, 3, 1, 5, 6))

fun sortArray(nums: IntArray): IntArray {
    mergeSort(nums, 0, nums.size - 1)
    return nums
}

fun mergeSort(nums: IntArray, left: Int, right: Int) {
    if (right <= left) return
    val mid = (left + right) / 2

    mergeSort(nums, left, mid)
    mergeSort(nums, mid + 1, right)

    merge(nums, left, right)
}

fun merge(nums: IntArray, leftIndex: Int, rightIndex: Int) {
    val mid = ((leftIndex + rightIndex) / 2)
    val intArray = IntArray((rightIndex - leftIndex) + 1)
    var leftPointer = leftIndex
    var rightPointer = mid + 1
    var currentTempIndex = 0

    while (leftPointer <= mid && rightPointer <= rightIndex) {
        if (nums[leftPointer] > nums[rightPointer]) {
            intArray[currentTempIndex] = nums[rightPointer]
            rightPointer++
            currentTempIndex++
        } else {
            intArray[currentTempIndex] = nums[leftPointer]
            leftPointer++
            currentTempIndex++
        }
    }

    while (leftPointer <= mid) {
        intArray[currentTempIndex] = nums[leftPointer]
        leftPointer++
        currentTempIndex++
    }

    while (rightPointer <= rightIndex) {
        intArray[currentTempIndex] = nums[rightPointer]
        rightPointer++
        currentTempIndex++
    }

    for (i in leftIndex..rightIndex) {
        nums[i] = intArray[i - leftIndex]
    }
}