[LeetCode] 454 - 4Sum II

LeetCode Problem Link: https://leetcode.com/problems/4sum-ii/description/

Sol: 

class Solution {
    public int fourSumCount(int[] A, int[] B, int[] C, int[] D) {
        Map<Integer, Integer> sumABMap = new HashMap();
        for (int i = 0; i < A.length; i++) {
            for (int j = 0; j < B.length; j++) {
                int sum = A[i] + B[j];
                sumABMap.put(sum, sumABMap.getOrDefault(sum, 0) + 1);
            }
        }
        
        int touples = 0;
        for (int i = 0; i < C.length; i++) {
            for (int j = 0; j < D.length; j++) {
                touples += sumABMap.getOrDefault(-C[i] - D[j], 0);
            }
        }
        
        return touples;
    }

}

Complexity:
O(n^2) time complexity (Compute the sum of AB and CD.)
O(n^2) space complexity (Store the sum of A and B)

Result:
Runtime: 132ms
Beats 98.25% users.