Display Table of Food Orders in a Restaurant LeetCode solution in C++

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class Solution {
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 public:
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  vector<vector<string>> displayTable(vector<vector<string>> &orders) {
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    vector<vector<string>> ans;
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    map<int, map<string, int>> m;
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    set<string> s; // Sets are useful as they dont contain duplicates as well
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                   // arranges the strings in order.
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    for (auto row : orders)
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    {
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      s.insert(row[2]);
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      m[stoi(row[1])][row[2]]++;
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    }
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    vector<string> dem;
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    dem.push_back("Table");
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    for (auto a : s)
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    {
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      dem.push_back(a);
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    } // For the  first row only
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    ans.push_back(dem);
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    for (auto it : m)
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    {
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      vector<string> row;
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      row.push_back(to_string(it.first));
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      auto dummy = it.second;
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      for (auto st : s) // we use set here as it has food names stored in asc order.
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      {
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        row.push_back(to_string(dummy[st])); // we access the number of orders.
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      }
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      ans.push_back(row);
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    }
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    return ans;
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  }
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};