View Compilation Error

0_0_25644714_12473.cpp: In function 'int main()':
0_0_25644714_12473.cpp:45:25: error: invalid types 'std::vector<query> [200000][__gnu_cxx::__enable_if<true, double>::__type {aka double}]' for array subscript
         lst[sqrt(Q[i].k)].push_back(Q[i]);
                         ^