Initialized the constructor of BST()
Implemented private size() and public size()

Not sure if they would work. Still need to test them.
Implemented add() and debugged previous methods

Should have used "NULL" instead of "null";
Implemented find() methods

Haven't tested them yet. Need to do that.
Implemented find()
Implemented remove() methods and max()

Haven't tested them yet. Need to do it.
Debugged delete() and commented it

Since it was implemented based on class notes, I needed to comment it to
make sure I knew what I was doing.
Implmented min()
Implemented next()

Haven't tested them yet. Need to do that.
Did most exercises
Debugged next() and implemented prev()
Tried to debugged my code
Tried to debug prev() and add()
Debugged two find() methods and two add() methods
Tried to debug two next() and two prev() methods
Changed something
Merge pull request #31 from YangLi1/master

None