title: C++: vector<vector<int>> iterator?
body: <p>Just have some basic question regarding c++ iterators. </p>
  
  <p>Say I have a object <code>vector&lt;vector&lt;int&gt;&gt; vec2d</code>.</p>
  
  <pre><code>vector&lt;vector&lt;int&gt;&gt;::iterator i, iEnd;
  i = vec2d.begin();
  iEnd = vec2d.end();
  </code></pre>
  
  <p>I am wondering if <code>i</code> is an iterator of an entire 1D array? </p>
  
  <p>what is that <code>(*i) [1]</code> mean?</p>