bx03_bubble_sort

def bubble_sort(li):

    # 排序 n-1 趟
    for i in range(len(li) - 1):
        exchange = False
        for j in range(len(li) - i - 1):
            if li[j] > li[j + 1]:
                li[j], li[j + 1] = li[j + 1], li[j]
                exchange = True

        # 每一趟结束后，检验有没有交换
        if not exchange:
            return