Copy content of one STL container to another
<p>How could I create a copy of an unordered_map from an existing one? Could I use assignment operator or I need to iterate it one by one?
Also, I am using shared_ptr as the value in the map. Did I need to take extra care because it is shared_ptr?</p>

<pre><code>typedef unordered_map&lt;string, shared_ptr&lt;classA&gt;&gt;MAP1;
MAP1 map1;
map1["abc"] = make_shared&lt;classA&gt;();
MAP2 map2 = map1; ?? //can I use assignment operator??
</code></pre>

<p>Thanks.</p>
