Account Merge GFG

class DisjoinSet{
    vector<int> rank, parent, size;
public:
    DisjoinSet(int n){
        rank.resize(n+1, 0);
        parent.resize(n+1);
        size.resize(n+1);
        for(int i=0;i<=n;i++){
            parent[i] = i;
            size[i] = 1;
        }
    }
    int findUPar(int node){
        if(node == parent[node]) return node;
        return parent[node] = findUPar(parent[node]);
    }
    void unionByRank(int u, int v){
        int ultimateParent_u = findUPar(u);
        int ultimateParent_v = findUPar(v);
        if(ultimateParent_u == ultimateParent_v) return;
        if(rank[ultimateParent_u] < rank[ultimateParent_v]){
            parent[ultimateParent_u] = ultimateParent_v;
        }
        else if(rank[ultimateParent_v] < rank[ultimateParent_u]){
            parent[ultimateParent_v] = ultimateParent_u;
        }
        else{
            parent[ultimateParent_v] = ultimateParent_u;
            rank[ultimateParent_u]++;
        }
    }
    void unionBySize(int u, int v){
        int ultimateParent_u = findUPar(u);
        int ultimateParent_v = findUPar(v);
        if(ultimateParent_u == ultimateParent_v) return;
        if(size[ultimateParent_u] < size[ultimateParent_v]){
            parent[ultimateParent_u] = ultimateParent_v;
            size[ultimateParent_v] += size[ultimateParent_u];
        }
        else{
            parent[ultimateParent_v] = ultimateParent_u;
            size[ultimateParent_u] += size[ultimateParent_v];
        }
    }

};
class Solution{
  public:
    vector<vector<string>> accountsMerge(vector<vector<string>> &accounts) {
        // code here
        int n = accounts.size();
        DisjoinSet ds(n);
        unordered_map<string, int> mapMailNode;
        for(int i=0;i<n;i++){
            for(int j=1;j<accounts[i].size();j++){
                string mail = accounts[i][j];
                if(mapMailNode.find(mail) == mapMailNode.end()){
                    mapMailNode[mail] = i;
                }
                else{
                    ds.unionBySize(i, mapMailNode[mail]);
                }
            }
        }
        vector<string> mergedMail[n];
        for(auto it: mapMailNode){
            string mail = it.first;
            int node = ds.findUPar(it.second);
            mergedMail[node].push_back(mail);
        }
        vector<vector<string>> ans;
        for(int i=0;i<n;i++){
            if(mergedMail[i].size() == 0) continue;
            sort(mergedMail[i].begin(), mergedMail[i].end());
            vector<string> temp;
            temp.push_back(accounts[i][0]);
            for(auto it: mergedMail[i]) temp.push_back(it);
            ans.push_back(temp);
        }
        return ans;
    }
};