def quick_sort(alist, first, last):
    if first >= last:
        return
    mid_value = alist[first]
    low = first
    high = last
    while low < high:
        while low < high and alist[high] >= mid_value:
            high -= 1
        alist[low] = alist[high]

        while low < high and alist[low] < mid_value:
            low += 1
        alist[high] = alist[low]

    alist[low] = mid_value
    quick_sort(alist, first, low-1)
    quick_sort(alist, low+1, last)


li = [17, 54, 26, 66, 29]
print(li)
quick_sort(li, 0, len(li) - 1)
print(li)
#最优时间复杂度O(nlogn)
#最坏时间复杂度O(n^2)
#不稳定