QuickSort.swift

extension Array {
    func quickSorted(_ areInIncreasingOrder: (Element, Element) -> Bool) -> Array {
        guard count > 1, let lastElement = last else { return self }
        var (preceding, successing) = (Array(), Array())
        dropLast().forEach { areInIncreasingOrder($0, lastElement) ? preceding.append($0) : successing.append($0) }
        return preceding.quickSorted(areInIncreasingOrder) + [lastElement] + successing.quickSorted(areInIncreasingOrder)
    }
}