title: iterators after element deletion in cpp
body: <p>In c++  , what happens to the iterators when an element is added or deleted.</p>
  <p>For example, vector is  :{1,2,3,4,5,6}
  and suppose two iterators a and b point to element '2', and '5'.
  If I delete 3rd item i.e. delete '3', what will the iterators be pointing to ?</p>
  <p>And if the iterator points to the last element, and that element gets deleted, will it cause error? I need to implement this code, where the elements are randomly deleted, i wanted to know the best /suitable data structure in which references doesn't change after the insertion ordeletion.</p>