[220203] 4Sum ll

from collections import defaultdict


class Solution:
    def fourSumCount(self, nums1, nums2, nums3, nums4):

        mp = defaultdict(int)
        count = 0

        # 先做 nums1 + nums2
        for i in nums1:
            for j in nums2:
                mp[i + j] += 1

        # nums3 + nums4 取相反数
        for k in nums3:
            for l in nums4:
                count += mp[-(k + l)]

        return count