Programming  Assignment 2.                   Nov 17 2015

1.  Write a C++ program to implement a version of Vector using AVL trees.
Use pointer implementation.  Zero points otherwise.
Additional information will be provided during regular class hours.

Operations on the tree are:

elementAtRank(r) : return the element at rank r, error if out of bounds
replaceAtRank(r,e):  replace element at rank r by e, error if out of bounds
insertAtRank(r,e):  insert e at rank r;  elements currently at rank r or above
                     are pushed up by 1 in rank, error if out of bounds
removeAtRank(r): delete element at rank r; elements currently at rank r or above 
                 are pushed down by 1 in rank, error if out of bounds
printAll():  print elements by rank.

You may assume that the type of e is int.

IMPORTANT:  You are not allowed to share codes, copy from any printed
source or internet.  Please see the handout regarding cheating.
We will talk about these operations in the class.