Group the People Given the Group Size They Belong To

class Solution {
public:
    vector<vector<int>> groupThePeople(vector<int>& groupSizes) {
        vector<vector<int>>v;
        int n=groupSizes.size();
        vector<vector<int>>x(n+1);
        for(int i=0;i<n;i++)
        {
            x[groupSizes[i]].push_back(i);
            if(x[groupSizes[i]].size()==groupSizes[i])
            {
                v.push_back(x[groupSizes[i]]);
                x[groupSizes[i]].clear();
            }
        }
        return v;
    }
};