454-mulmuri.py

class Solution:
    def fourSumCount(self, A: List[int], B: List[int], C: List[int], D: List[int]) -> int:
        dicA = {}
        dicB = {}
        dicC = {}
        dicD = {}

        for i in A:
            if i in dicA.keys():
                dicA[i] += 1
            else:
                dicA[i] = 1;
        for i in B:
            for j in dicA.keys():
                if i+j in dicB:
                    dicB[i+j] += dicA[j]
                else:
                    dicB[i+j] = dicA[j]

        for i in C:
            if i in dicC.keys():
                dicC[i] += 1
            else:
                dicC[i] = 1;
        for i in D:
            for j in dicC.keys():
                if i+j in dicD:
                    dicD[i+j] += dicC[j]
                else:
                    dicD[i+j] = dicC[j]

        ans = 0;
        for i in dicD.keys():
            if -i in dicB.keys():
                ans += dicB[-i]*dicD[i]
        return ans