message: Update number-of-atoms.cpp
diff: @@ -7,14 +7,14 @@ public:
  stack<map<string, int>> stk;
  stk.emplace();
  int submatches[] = { 1, 2, 3, 4, 5 };
  - auto e = regex("([A-Z][a-z]*)(\\d*)|(\\()|(\\))(\\d*)");
  + const auto e = regex("([A-Z][a-z]*)(\\d*)|(\\()|(\\))(\\d*)");
  for (regex_token_iterator<string::iterator> it(formula.begin(), formula.end(), e, submatches), end;
  it != end;) {
  - auto name = (it++)->str();
  - auto m1 = (it++)->str();
  - auto left_open = (it++)->str();
  - auto right_open = (it++)->str();
  - auto m2 = (it++)->str();
  + const auto& name = (it++)->str();
  + const auto& m1 = (it++)->str();
  + const auto& left_open = (it++)->str();
  + const auto& right_open = (it++)->str();
  + const auto& m2 = (it++)->str();
  if (!name.empty()) {
  stk.top()[name] += stoi(!m1.empty() ? m1 : "1");
  }
  