View Compilation Error

0_0_37849600_31975.cpp: In function 'void DFS(long long int, long long int, long long int)':
0_0_37849600_31975.cpp:37:39: error: 'sort' was not declared in this scope
  sort(vec[cur].begin(), vec[cur].end());
                                       ^
0_0_37849600_31975.cpp:70:14: error: 'assert' was not declared in this scope
   assert(L<=R);
              ^