title: How to merge 2 std::maps, and output the result in a 3rd map
body: <p>Editing the original question, as I wanted to ask question about <code>std::map</code>, instead of <code>std::vector</code>. My mistake. Sorry.</p>
  
  <p>My data is actually in 2 <code>std::map</code>s. I want to merge both the maps into a 3rd map.</p>
  
  <p>My first and second maps contain entries with the same key. So I would like to merge data under those keys as well, into my resultant 3rd map.</p>
  
  <p>So if I use <code>std::merge</code>, will I be loosing data from the first or second maps common entries? As I have mentioned that there are common data (values) in both the maps?</p>