title: C++ multidimensional map: How to acces 'inner' maps?
body: <p>I have a multidimensional map. Lets say:</p>
  
  <pre><code>std::map&lt;std::string, 
      std::map&lt;std::string, 
          std::map&lt;std::string, std::list&lt;std::string&gt;&gt;&gt;&gt; my_map;
  </code></pre>
  
  <p>My question is: What is the proper way to get access to the 'inner' maps (the objects)? I do not talk about the values. I know they can be accessed via </p>
  
  <pre><code>my_map["key1"]["key2"]....
  </code></pre>
  
  <p>I mean the size for example. How do I get the size of the second map. Is this the right way to do it?:</p>
  
  <pre><code>my_map.begin()-&gt;second.size()
  </code></pre>