molecules.cpp:19:22: error: 'istream' does not name a type
19 | template<typename T> istream& operator>>(istream& in, vector<T>& a) {for(auto &x : a) in >> x; return in;};
| ^~~~~~~
molecules.cpp:20:22: error: 'ostream' does not name a type
20 | template<typename T> ostream& operator<<(ostream& out, vector<T>& a) {for(auto &x : a) out << x << ' '; return out;};
| ^~~~~~~
molecules.cpp:4:11: error: 'vector' does not name a type
4 | #define V vector
| ^~~~~~
molecules.cpp:22:1: note: in expansion of macro 'V'
22 | V<int> find_subset (int l, int u, V<int> w) {
| ^