Notes

Outline

Data Structures Topic #1 Welcome!

Today’s Agenda Introduction...what to expect!?! Talk about our Goals and Objectives Textbook is highly recommended Lecture Notes at clean copy Discuss what Assignments will be like This week is mostly review, so we will go rather rapidly through the material...and then slow down

Programming Paradigms Procedural Abstraction Modular Abstraction Data Abstraction Object Oriented Programming

Data Structures Our goal this term is to spend our time talking about different data structures, algorithms to solve problems, and how to measure the efficiency of the approaches taken This term is not about learning new C++ syntax! Instead, we will apply C++ and linked lists to new abstract data types

Data Structures vs. ADT? So, what is the difference between a data structure and an abstract data type? A data structure specifies how we store the data  (like an array, linked list) An abstract data type (ADT) specifies how a new data type behaves: it includes the data and operations that the new data type requires; the data being stored in a data structure!

Data Structures vs. ADT? We will be building Abstract Data Types all term! Let’s walk thru some examples of ADTs int list stack queue

Data Structures vs. ADT? So, what is the difference between: Data Abstraction Abstract Data Type Data Structure Client vs. Client Program User vs. Application

Using Classes to build ADTs We will use the C++ class construct to build abstract data types The data (represented by a data structure) are placed in the private section The operations (what the “client” or application can do) is in the public section

Using Classes to build ADTs The user & client should not be aware of what data structure is being used This means the client program should not be aware that there is a node or a next pointer for a linked list, or an index to an array -- if an array is used This allows an ADT to “plug and play” different data structures, to maximize efficiency w/o disrupting the client program

Using Classes to build ADTs Given this, what do you think we should do about: data members? error messages? input of data? output of data? prompting?

Using Classes to build ADTs For each data member, ask yourself the question....could this be a local variable to a member function instead? If the value of the variable does not need to persist from operation to operation, it should not be a data member!

Using Classes to build ADTs The client program represents... your “test bed” or the “application program” represented by your main program Keep your data members restricted to just what is necessary Classes should not prompt For 163, classes should also not perform input...we will change that in CS 202

Using Classes to build ADTs The main program is the only place you should use statically allocated (do you remember what this term means?) arrays All arrays must be dynamically allocated in your class...why? Think about the when an ADT is written vs. an application. The ADT should be able to be used by many applications...

Using Classes to build ADTs Try to make your ADT’s as general as possible (without getting into templates). This means don’t tie the member functions to reading information from the keyboard Because...the ADT doesn’t know if there is anyone AT the keyboard!!!

Using Classes to build ADTs Use arguments instead and have the main() read from the keyboard (and prompt) This way, information can come from the keyboard or a file!!! And, of course, no global variables are allowed And, never prompt from a member function! Think of an int prompting!!!!!

Using Classes to build ADTs Think about Efficiency Too this term! Only traverse lists when absolutely necessary Use pass by reference to reduce the information from continually being copied -- when passing instances of a struct or a class And, remember to wear “different hats”