Question

我有一个来自表查找的int迭代器，需要检查他们的multiset是否包含在给定的固定＆＃34; multiset＆＃34; ms。目前，我在开头对ms进行排序，然后在我的迭代器中对int进行排序，并按如下方式检查多重包含（排序列表）：

vals = sorted(my_vals)
for it in ... :
    test_vals = sorted( i for i in it )
    if is_sublist(test_vals,vals):
        # do stuff

，其中

def is_sublist(L1,L2):
    m = len(L1)
    n = len(L2)
    i = j = 0
    while j <= n:
        if i == m:
            return True
        elif j == n:
            return False
        a,b = L1[i], L2[j]
        if a == b:
            i += 1
            j+= 1
        elif a > b:
            j += 1
        else:
            return False

通常，我的名单很短（1-20个元素）
我尝试使用Counter，但其初始化的时间劣势比收容测试的时间优势更差。
我这样做~10 ^ 6次，所以我应该在cython

任何想法或指示都会很好 - 谢谢！（抱歉先过早点击发布按钮...）

Answer 1

# edit: second attempt in response to Bakuriu's comment
#
from collections import Counter
from itertools import groupby
multiset = Counter(sorted(vals)) # only create one Counter object
for it in ...:
    grouped = groupby(sorted(it))
    if all(len(list(g)) <= multiset[k] for k, g in grouped):
        # do stuff



from operator import eq
# if you are using Python 2
from itertools import izip as zip
from itertools import starmap

vals = sorted(my_vals)
for it in ...:
    test_vals = sorted(it)
    zipped = zip(test_vals, vals)
    # check if test_vals' multiset is contained 
    # in vals' multiset but bale out as soon as
    # non-matching values are found.
    if all(starmap(eq, zipped)):
        # do stuff

快速multiset包含python中的列表

1 个答案: