JavaScript-there is an array from which to pick ABC three integers, so that the ABC three integers equals 0, see how many such arrays?

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Typical 3sum,leetcode have the original problem https://leetcode.com/problems ...

JavaScript can look at my https://github.com/hanzichi/l ...

This problem is also the staff of the introduction of the Lao Zhao and winter handwritten questions, you can see the https://zhuanlan.zhihu.com/p/...

The best approach seems to be that both sides of O (n^2) are forced into

are sure to be 3 integers ... Direct Triple-Loop enumeration ah .....

As @xiaoboost says, the simple act of violence can be used:

import itertoolsdef nsum(lst, n, target):    count = 0    for c in itertools.combinations(lst, n):        if sum(c) == target:            count += 1    return countif __name__ == '__main__':    lst = [-1, 3, -2, 7, -4, -3, 6, 9, -2, -2, 1, 1, 0, 10, -1, 9, 8, -12]    print(nsum(lst, 3, 0))

Results:

22

I answered the question: Python-qa

from itertools import combinationsdef sum_is_sth(lst, sth=0, cnt=3):    return sum([1 for sub_lst in combinations(lst, cnt) if sum(sub_lst) == sth])

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