title: how is push_back implemented in STL vector?
body: <p>I was asked this question in an interview. </p>
  
  <p>The points I answered are like this</p>
  
  <p>1) an index pointing to the current position;</p>
  
  <p>2) resize if neccessary.</p>
  
  <p>Can anybody elaborate more?</p>