title: Does allocating memory multiple times takes more time in one go?
body: <p>As we all know, a sequence container's (except lists') capacity is implementation-defined after <code>push_back</code> to a container which its <code>capacity</code> is equal to its <code>size</code>?</p>
  
  <p>And most of the complier will reserve more momery rather than just allocate one more size and keep capacity equal to size.</p>
  
  <p>So I think that allocate multiple times will take more time. But except checking <code>bad_alloc</code>, are there other reasons?</p>