Comparing unordered_map vs unordered_set : <p>First of all, what is the main difference between them? </p>

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

<p>Which container is using random access to memory(or both)?</p>

<p>And which one of them faster in any sense or using less memory?</p>
