Project 3 Solution

Goal



To explore an advanced application of priority queues in order to gain a deeper understanding of the data structure.

Background



You will be writing a basic application to help a user select a car to buy. You will write a menu-based user interface driver program (to be run in the terminal, no GUI), but most of the logic will be in implementing a priority queue-based data structure. You should write a PQ-based data structure that stores objects according to the relative priorities of two of their attributes, making it efficient to retrieve objects with the minimum value of either attribute. Your data structure should further be indexable to allow for efficient updates of entered items. You will want users to be able to enter details about cars that they are considering buying. The user should then be able to efficiently retrieve the car with the lowest mileage or lowest price. These retrievals should be possible on the set of all entered cars or on the set of all cars of a specific make and model (e.g., “lowest price Ford Fiesta”, “lowest mileage Cadillac Escalade”).

Specifications



    1. First, you must create a class to store data about cars to buy. Specifically, this class must contain the following information:

A unique VIN number: a 17-character string of numbers and capital letters, excluding I (i), O (o), or Q


    (q) to avoid confusion with numerals 1 and 0 The car’s make (e.g., Ford, Toyota, Honda) The car’s model (e.g., Fiesta, Camry, Civic) The price to purchase (in dollars)

The mileage of the car

The color of the car


    2. You must write a terminal menu-based driver program (again, no GUI). Specifically, your driver must present the user with the following options:

1.  Add a car

This will prompt the user for each of the above-listed attributes of a car to keep track of.


2.  Update a car

This option will prompt the user for the VIN number of a car to update, and then ask the user if they would like to update 1) the price of the car, 2) the mileage of the car, or 3) the color of the car


3.  Remove a specific car from consideration

This option will prompt the user for the VIN number of a car to remove from the data structure (e.g., if it is no longer for sale)

Note that this mean you will need to support removal of cars other than the minimum (price or mileage) car


    4. Retrieve the lowest price car

    5. Retrieve the lowest mileage car

    6. Retrieve the lowest price car by make and model

This option will prompt the user to enter a make followed by a model, and then return the car with the minimum price for that make and model.


7.  Retrieve the lowest mileage car by make and model

This option will prompt the user to enter a make followed by a model, and then return the car with the minimum mileage for that make and model.


Note: Retrieval operations should not remove the car with minimum price or mileage from the data structure, just return information about that car. Cars should only be removed via the “remove a specific car from consideration” menu option.

3.    To aid in the testing of your application, you will find example files with some test data stored in your folder ( cars.txt and cars2.txt ). Your progam should read in the contents of this file to initialize your data structure each time it is run. You can assume that this file will already exist, and you do not need to write an updated version of the data structure back to the file.


    4. To ensure efficiency of operations, you must base your data structure around the use of heaps with indirection (making them indexable). Note that retrieval operations on either attribute (e.g., retrieve minimum price, retrieve minimum mileage) must have a O(log n) runtime (both for all cars, and for a specific make and model). Updates and removals must also have a O(log n) runtime. Take care in
selecting your approach (especially the indirection data structure) to account for the types of keys you will need to store and the type and number operations that you will need to perform on them.

    5. Because this project requires you to make a number of decisions about how to implement its requirements, write a documentation file explaining your implementation and justifying your decisions.
Name this file documentation.txt . Document your approach carefully, to reduce the effort required to trace through your code during grading. State the runtime and memory requirements of your approach, and use this information as part of your explanation of why you chose your approach.


Submission Guidelines



Upload your submission to the provided Box folder named cs1501-p3-abc123 , where abc123 is your Pitt username.

DO NOT upload any IDE package files.


You must name the primary driver for your program CarTracker.java , and it must be outside of any package.

You must be able to compile your program by running    javac CarTracker.java .


You must be able to start your program by running    java CarTracker


You must document and justify your approach in    documentation.txt .


You must fill out    info_sheet.txt .


The project is due at the precise date and time stated above. Upload your progress to Box frequently, even far in advance of this deadline. No late assignments will be accepted. At the deadline, your Box folder will automatically be changed to read-only, and no more changes will be accepted. Whatever is present in your Box folder at that time will be considered your submission for this assignment—no other submissions will be considered.


Additional Notes and Hints



You are allowed to use code provided by the book authors in implementing your solution. It is up to you to decide if it would be easier to modify the provided code to meet the requirements of this project or to start with a clean slate with entirely your own code.


To make testing your program easier, you do not need to enforce that users enter properly-formatted VIN numbers. However, your data structure should be designed to operate efficiently on VIN numbers formatted as specified here.


You may consider adding additional rows to cars.txt to expand your testing. During grading, we will test by placing other data in cars.txt , so you should be sure your code works for a wide variety of scenarios and corner-cases.

Grading Rubric



Feature
Points
Adding a car works properly
10
Updating a car works properly
10
Removing a car works properly
15
Retrieval for all cars works properly
10
Retrieval for a given make/model works properly
15
Operations on either attribute are efficient due to heap-backed data structure
15
Validity of justifications
15
Menu-based driver program works properly and has appropriately labeled options
5
Assignment info sheet/submission
5