Group the People Given the Group Size They Belong To LeetCode solution in C++

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class Solution {
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 public:
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  vector<vector<int>> groupThePeople(vector<int> &groupSizes) {
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    vector<vector<int>> ans;
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    unordered_map<int, vector<int>> store;
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    for (int i = 0; i < groupSizes.size(); i++) {
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      if (store[groupSizes[i]].size() == groupSizes[i]) {
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        ans.push_back(store[groupSizes[i]]);
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        store[groupSizes[i]].clear();
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      }
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      store[groupSizes[i]].push_back(i);
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    }
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    for (auto &x : store) {
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      ans.push_back(x.second);
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    }
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    return ans;
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  }
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};