Comparing unordered_map vs unordered_set

Question

First of all, what is the main difference between them?

The only thing i've found is that unordered_set has no operator []. How should i access an element in unordered_set, since there is no []?

Which container is using random access to memory(or both)?

And which one of them faster in any sense or using less memory?

Answer 1

They are nearly identical. unordered_set only contains keys, and no values. There is no mapping from a key to a value, so no need for an operator[]. unordered_map maps a key to a value.

You can use the various find methods within unordered_set to locate things.

Answer 2

you can use iterators to access elements.

unordered_set <string> u{
            "Dog",
            "Cat",
            "Rat",
            "Parrot",
            "bee"
};

for(auto& s:u){
     cout << s << ' ';    
} 

unordered_set<string>::const_iterator point = u.find("bee");