1418.cpp

class Solution {
  public:
    vector<vector<string>> displayTable(vector<vector<string>> &orders) {
        map<int, vector<string>> tables;
        vector<vector<string>> res;
        set<string> foods;

        for (const auto &order : orders) {
            tables[stoi(order[1])].push_back(order[2]);
            foods.insert(order[2]);
        }

        unordered_map<string, int> pos;

        int j = 1;
        res.push_back({{"Table"}});
        for (auto &food : foods) {
            res[0].push_back(food);
            pos[food] = j++;
        }

        for (auto &[table, foods] : tables) {
            vector<int> row(res[0].size(), 0);
            vector<string> rows;
            rows.reserve(res[0].size());
            for (const auto &food : foods)
                row[pos[food]]++;
            row[0] = table;
            for (int r : row)
                rows.push_back(to_string(r));
            res.push_back(rows);
        }

        return res;
    }
};