Insert new element into hash table? - c++

Question

auto iterator = unorderedMap.find(element);
if (iterator == unorderedMap.end()) { //If the element doesn't already exist in the table, create a new entry
iterator = unorderedMap.insert(make_pair((element), vector<unsigned>()).first;
}
iterator->second.push_back(unsigned_number_associated_with_element);
The hashtable is a table of strings and vector<unsigned> (the key is of type string).
element is of type of string.
The code is supposed to do the following:
1) Check if the key element exists in the hash table
2) If it doesn't, create a new entry. If it does, just do the next step.
3) Push element into the entry's vector.
The code compiles fine, but running it gives me an error:
error: attempt to subscript container
with out-of-bounds index 22464, but container only holds 22464 elements
Anyone know why? Commenting out the last line makes the error go away.

Answer 1

I honestly don't know where that error was coming from (although I suspect that it was some sort of unfortunate parenthesization error), but there is no difference between the intent of that code and the following rather simpler code:
unorderedMap[element].push_back(unsigned_number_associated_with_element);
except that the above is probably faster (it will only do one lookup rather than two if the element isn't present) and is certainly easier to read and debug.