meeting rooms ||

int sz = intervals.size();

        vector <int> starts(sz,1);
        vector <int> ends(sz, 1);



        for (int i = 0 ; i < sz ; i++ )
        {
            starts[i] = intervals[i][0];
            ends[i] = intervals[i][1];
        }

        sort(starts.begin(), starts.end());
        sort(ends.begin(), ends.end());


        int res = 0;
        int e = 0;
        for (int i = 0 ; i < sz ; i++ )
        {
            if (ends[e] > starts[i])
                res++;
            else
                e++;

        }
        return res;