def quick_sort(l):
    def partition(l, left, right):
        i, j, pivot = left, right - 1, l[left]
        while i != j:
            while i < j and pivot <= l[j]:
                j -= 1
            l[i] = l[j]
            while i < j and pivot >= l[i]:
                i += 1
            l[j] = l[i]

        l[i] = pivot
        return i

    def quick_sort_rec(l, left, right):
        pi = partition(l, left, right)
        if pi - left > 1:
            quick_sort_rec(l, left, pi)
        if right - pi > 2:
            quick_sort_rec(l, pi + 1, right)

    if l:
        quick_sort_rec(l, 0, len(l))