冒泡排序（优化后）

优化过的冒泡排序(搅拌排序)也称鸡尾酒排序：

def bubble_sort(alist, comp=None):
    """优化过的冒泡排序(搅拌排序)"""
    for i in range(len(alist) - 1):
        swapped = False
        for j in range(len(alist) - 1 - i):
            comp_result = comp(alist[j], alist[j + 1]) > 0 if comp else alist[j] > alist[j + 1]
            if comp_result:
                alist[j], alist[j + 1] = alist[j + 1], alist[j]
                swapped = True
        if swapped:
            swapped = False
            for j in range(len(alist) - 2 - i, 0, -1):
                comp_result = comp(alist[j], alist[j - 1]) < 0 if comp else alist[j] < alist[j - 1]
                if comp_result:
                    alist[j], alist[j - 1] = alist[j - 1], alist[j]
                    swapped = True
        if not swapped:
            break

• comp:一个规定排序规则的函数