C++: Accounts Merge

class Solution {
public:
    // find method is using path compression
    // With path compression, instead of following the chain every time, 
    // we make each email directly point to the root when we find it. 
    // This way, next time it's an  instant lookup.
    string find(unordered_map<string, string> &parentMap, string email) {

        if (parentMap[email] != email) {
            parentMap[email] = find(parentMap, parentMap[email]);
        }
        return parentMap[email];

        // Traditional find method.
        // while(parentMap[email]!=email)
        //     email = parentMap[email];
        
        // return parentMap[email];
    }
    vector<vector<string>> accountsMerge(vector<vector<string>>& accounts) {

        unordered_map<string, string> mailToPerson; // Mail --> Person
        unordered_map<string, string> parentMap;    // Stores Parent of Each Email
        unordered_map<string, set<string>> parentToAllEmails; // ParentEmail --> All Emails
        vector<vector<string>> ans; // To store the answer in desired format.

        // Step-1: Initialization
        for (int i = 0; i < accounts.size(); i++) {

            for (int j = 1; j < accounts[i].size(); j++) {

                mailToPerson.insert({accounts[i][j], accounts[i][0]});
                parentMap[accounts[i][j]] = accounts[i][j]; // Initially, each email points to itself.
            }
        }

        // Step-2: Assign Parents (Union Operation)
        for (int i = 0; i < accounts.size(); i++) {

            string parentOfFirstEmail = find(parentMap, accounts[i][1]);  // Find parent of first email 
            for (int j = 2; j < accounts[i].size(); j++) {

                string parentOfOtherEmails = find(parentMap, accounts[i][j]);
                parentMap[parentOfOtherEmails] = parentOfFirstEmail;
            }
        }

        // Step-3: Group Emails under their Parent
        for (vector<string> entity : accounts) {

            string parentOfFirstEmail = find(parentMap, entity[1]);
            for (int i = 1; i < entity.size(); i++) {
                parentToAllEmails[parentOfFirstEmail].insert(entity[i]);
            }
        }

        // Step-4: Build the result in the required format.
        for (auto itr = parentToAllEmails.begin(); itr != parentToAllEmails.end(); itr++) {

            string personName = mailToPerson[itr->first];
            set<string> emails = itr->second;

            vector<string> mergedAccount(emails.begin(),emails.end());
            mergedAccount.insert(mergedAccount.begin(), personName);
            ans.push_back(mergedAccount);
        }
        return ans;
    }
};