title: vector of vectors push_back
body: <p>I'm designing a multilevel queue process simulator in C++ but I've got a problem when trying to implement several queues (my queues are vectors).So,
  "multilevel" is a 4 elements array (not vector). Inside each of those elements there is a vector (type t_PCB). </p>
  
  <pre><code>vector&lt;vector&lt;t_PCB&gt;&gt; multilevel[4];
  </code></pre>
  
  <p>My question is: How can i insert an element at the end of one these 4 <code>t_PCB</code> vectors? Thank you in advance.</p>
  
  <p>I've tried the code line below but it doesn't work (<strong>error</strong>: not matching member function for call 'push_back')</p>
  
  <pre><code>multilevel[0].push_back(p); //where "p" is a t_PCB object
  </code></pre>
  
  <p>The line from above can not be used when talking about "multilevel" because this array only accepts arguments type: vector &lt; t_PCB > </p>
  
  <p>So, as I ask at the beginning: how can I push an object type "t_PCB" inside "multilevel"?</p>