Swift code that flatten nested integer array for job application at citrusByte (you can exec this code and play with value in Xcode Playground)

flattenArray.swift

import Foundation

// nestedArrays will be a sample case to test our function
var nestedArrays = [[1,2,[3,[4,5]]],6] as [Any]

func flattenArray(nestedArrays array: [Any]) -> [Int]{
    var newArray = [Int]()
    array.forEach { item in
        // recursively check is array item is an array, if so, pass it to flattenArray func
        if let arrayItem = item as? [Any] {
        // I love Swift for the power of the if-let statement
            newArray = newArray + flattenArray(nestedArrays: arrayItem)
        } else {
            newArray.append(item as! Int)
        }
    }
    return newArray
}

let flatArray = flattenArray(nestedArrays: nestedArrays)