Question

Can we use forward iteration to erase elements in unordered_map ?

unordered_map<string, int> employeeTable;
unordered_map<string, int>::iterator it;

for (it = employeeTable.begin(); it != employeeTable.end();) {
   int age = it->second;
   if (age < 18) {
      employeeTable.erase(it++);
   } else {
      ++it;
   }
}

If the above is incorrect, what does the standard recommend ? Something like below

it = employeeTable.erase(it);

Answer 1

According to 6.3.1 [tr.unord.req] paragraph 12:

… The erase members shall invalidate only iterators and references to the erased elements.

That is, the code above should be OK.