LC2363. 合并相似的物品

class Solution {
public:
    vector<vector<int>> mergeSimilarItems(vector<vector<int>>& items1, vector<vector<int>>& items2) {
        map<int, int>a;
        for(auto item:items1) {
            a[item[0]] = item[1];
        }
        for(auto item:items2) {
            if (a.find(item[0]) == a.end()) {
                a[item[0]] = 0;
            }
            a[item[0]] += item[1];
        }
        vector<vector<int>> ans;
        for(auto aa=a.begin();aa!=a.end();aa++) {
            ans.push_back(vector{aa->first, aa->second});
        }
        return ans;
    }
};