title: What is the best way to concatenate two vectors?
body: <p>I'm using multitreading and want to merge the results. For example:</p>
  
  <pre><code>std::vector&lt;int&gt; A;
  std::vector&lt;int&gt; B;
  std::vector&lt;int&gt; AB;
  </code></pre>
  
  <p>I want AB to have to contents of A and the contents of B in that order. What's the most efficient way of doing something like this?</p>