import UIKit

extension Array {
    func duplicate(with array: Array) -> Array {
        var result = Array()
        for (key, value) in array.enumerated() {
            result.append(self[key])
            result.append(value)
        }

        return result
    }

    func duplicateBySelf() -> Array {
        return duplicate(with: self)
    }
}

let p = [ [ 1, 0 ], [ 2, 2 ], [3, 4] ]
let q = [ 1, 2, 3, 4 ]

p.duplicateBySelf()
q.duplicateBySelf()