721. Accounts Merge

https://leetcode.com/problems/accounts-merge/description/

class UnionFound {
public:
    unordered_map<int,int> parents;
    int cnt = 0;
    void AddItem(int i) {
        parents[i] = i;
        cnt++;
    }
    int GetParent(int i) {
        if (parents[i] == i)    return i;
        return parents[i] = GetParent(parents[i]);
    }
    void Union(int p, int c) {
        int pp = GetParent(p);
        int cp = GetParent(c);
        if (pp != cp) {
            parents[cp] = pp;
            cnt--;
        }
    }
};
class Solution {
public:
    vector<vector<string>> accountsMerge(vector<vector<string>>& accounts) {
        UnionFound uf;
        for (int i = 0; i < accounts.size(); i++)
            uf.AddItem(i);
        
        unordered_map<string, int> map_email_to_person;
        for (int i = 0; i < accounts.size(); i++)
            for (int j = 1; j < accounts[i].size(); j++) {
                const auto& email = accounts[i][j];
                if (map_email_to_person.count(email)) {
                    uf.Union(map_email_to_person[email], i);
                }
                else {
                    map_email_to_person[email] = i;
                }
            }
        
        unordered_map<int, set<string>> map_person_to_emails;
        for (int i = 0; i < accounts.size(); i++) {
            int person = uf.GetParent(i);
            for (int j = 1; j < accounts[i].size(); j++) {
                const auto& email = accounts[i][j];
                map_person_to_emails[person].insert(email);
            }
        }
        
        vector<vector<string>> res;
        for (const auto& it : map_person_to_emails) {
            vector<string> p;
            p.push_back(accounts[it.first][0]);
            for (const auto & email : it.second)
                p.push_back(email);
            res.push_back(p);
        }
        return res;
    }
};