Question

Whats the difference?

I want to be able to see if an element is in a HashMap and I just found out that if I do h[element], it will return the default element if it is not found, and not null. How would I use the iterator find method to see if the element is there?

Thanks

Answer 1

Assuming you’re talking about STL and not some 3rd party library… m[key] doesn’t just return the default object if key isn’t in the map. It will create a new element in the map with that key and a default-constructed object as value.

You could use this:

map<string, int> mymap;
//add items to it
map<string, int>::iterator it = mymap.find("key");
if (it != myMap.end()) {
    // 'key' exists; (it->second) is the corresponding int
}

Or if you don’t need to get the object (you just want to know if it exists):

map<string, int> mymap;
//add items to it
if (mymap.count("key") == 1) {
    // 'key' exists
}