private fun twoSome(nums: IntArray, target: Int): IntArray {
    val returnArray: IntArray = intArrayOf()
    var initialVal = nums[0]
    for (num in nums) {
        if (initialVal + num == target) {
            returnArray[0] = initialVal
            returnArray[1] = num
            break
        }
        initialVal = num
    }
    return returnArray
}

Why am I getting

ArrayIndexOutOfBoundsException

when assigning a value to the

returnArray

?

intArrayOf()

returns a 0-element array. You'd need

intArrayOf(0, 0)

. Since you only return two values here you might want a

Pair

.

What @Thomas said