/**
Scala implementation: flattening arbitrary nested arrays
*/
def flattenArray[T](input: Array[T]): Array[Int] = {
    input.flatMap {
        case a: Array[_] => flattenArray(a)
        case i: Int => Array(i)
    }
}

//some tests
val a = Array(3, Array(2, 3, 4), 6)
val b = Array()
val c = Array(Array(3,4,5), 1)
val d = Array(Array(3,4,Array(3)), 1)

flattenArray2(a)
flattenArray2(b)
flattenArray2(c)
flattenArray2(d)

// output:
//res0: Array[Int] = Array(3, 2, 3, 4, 6)
//res1: Array[Int] = Array()
//res2: Array[Int] = Array(3, 4, 5, 1)
//res3: Array[Int] = Array(3, 4, 3, 1)