查找表_leetcode454

# 解题思路：字典存储计数信息 20190302 找工作期间

class Solution(object):
    def fourSumCount(self, A, B, C, D):
        res2 = {}
        res = 0

        for i in C:
            for j in D:
                res2[i + j] = res2.get(i + j, 0) + 1

        for i in A:
            for j in B:
                res += res2.get(-i - j, 0)

        return res