Display Table of Food Orders in a Restaurant.cpp

class Solution {
public:
    string stoi(int a){
        if(a==0)
            return "0";
        string ret="";
        while(a!=0){
            int r=a%10;
            a/=10;
            ret+='0'+r;
        }
        reverse(ret.begin(),ret.end());
        return ret;
    }
    int ano(string s){
        int r=0;
        for(char c : s){
            r+=c-'0';
            r*=10;
        }
        return r/10;
    }
    vector<vector<string>> displayTable(vector<vector<string>>& o) {
        vector<vector<string>> ret;
        map<int,vector<string>> mp;
        set<string> st;
        for(auto it: o){
            mp[ano(it[1])].push_back(it[2]);
            st.insert(it[2]);
        }
        vector<string> temp;
        temp.push_back("Table");
        for(auto it : st)
            temp.push_back(it);
        ret.push_back(temp);
        map<string, int> fp;
        int num=0;
        for(auto it : st){
            fp[it]=num;
            num++;
        }
        for(auto it : mp){
            temp.clear();
            temp.push_back(stoi(it.first));
            vector<int> v(st.size());
            for(auto pp : it.second){
                v[fp[pp]]++;
            }
            for(auto pp : v)
                temp.push_back(stoi(pp));
            ret.push_back(temp);
        }
        return ret;
    }
};