title: Memcpy a 2-d vector
body: <p>Long story short, I have a 2-d vector that I need to memcpy().  How do I get a pointer to the first element of the data structure?</p>
  
  <p>Also, given that it's in continuous memory, I can just pass in this pointer and the total size, correct?</p>
  
  <p>Would the following code work?</p>
  
  <pre><code>vector &lt; vector &lt;int&gt; &gt; vec;
  //  .. assume it's populate and built up here
  int* ptr = vec[0].data();  // use this pointer
  </code></pre>