Leetcode -- addition of four numbers II

Add four numbers II

Topic link ： Add four numbers 2

Title Description

Topic analysis

Video analysis address ：B standing

Code

class Solution {
    
    public int fourSumCount(int[] nums1, int[] nums2, int[] nums3, int[] nums4) {
    
        HashMap<Integer,Integer> hashMap = new HashMap<>();
        int res = 0;
        for (int i : nums1) {
    
            for (int i1 : nums2) {
    
                int sum1 = i + i1;
                if (hashMap.containsKey(sum1)){
    
                    hashMap.put(sum1,hashMap.get(sum1)+1);
                }else {
    
                    hashMap.put(sum1,1);
                }
            }
        }

        for (int j : nums3) {
    
            for (int j1 : nums4) {
    
                int target = 0 - (j + j1);
                if (hashMap.containsKey(target)){
    
                    res += hashMap.get(target);
                }
            }
        }
        return res;

    }
}

Reference resources

https://programmercarl.com/0454.%E5%9B%9B%E6%95%B0%E7%9B%B8%E5%8A%A0II.html#%E5%85%B6%E4%BB%96%E8%AF%AD%E8%A8%80%E7%89%88%E6%9C%AC