Homework 2: Stacks and Queues Solution

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Description

Stacks and Queues

You are to code the following:

  1. A stack backed by a linked list

  1. A stack backed by an array

  1. A queue backed by a linked list

  1. A queue backed by an array

A queue is a rst-in, rst-out (FIFO) data structure. A stack is a last-in, rst-out (LIFO) data structure.

All of your data structures should implement the appropriate interface, either QueueInterface or StackInterface. Both interfaces de ne an initial capacity that you must use in your array implemen-tations; make sure to use the provided variable, not a magic number. Your linked list implementations should use the given head (and tail) pointer(s) to build the backing structure. Do NOT use Java’s linked list classes.

As always, these implementations must be as e cient as possible. Failure to do so will result in large point deductions.

Circular Arrays

The backing array in your ArrayQueue implementation must behave circularly. This means that when the user dequeues an element, you should simply treat the next index in the array as the new front. DO NOT SHIFT ANY ELEMENTS IN THE ARRAY. This also means that if there are empty

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Homework 2: Stacks and Queues Due: See T-Square

spaces at the front of the array, the back of the queue should wrap around to the front of the array and make use of those spaces.

When regrowing the backing array, realign the queue with the beginning of the new array during transfer, so that the front of the queue is once again at index 0. This is the ONLY time that the front of the queue should be reset. When dequeueing the last element in the queue, simply increment front as you normally would and leave it there. As far as your implement is concerned, enqueueing should be done using the back variable and dequeueing should be done using the front variable. Failure to do so will result in an implementation that cannot be graded correctly and will lead to large deductions.

Grading

Here is the grading breakdown for the assignment. There are various deductions not listed that are incurred when breaking the rules listed in this PDF, and in other various circumstances.

Methods:

ArrayQueue enqueue

15pts

ArrayQueue dequeue

10pts

LinkedQueue enqueue

10pts

LinkedQueue dequeue

10pts

ArrayStack push

12pts

ArrayStack pop

8pts

LinkedStack push

6pts

LinkedStack pop

4pts

Other:

Checkstyle

10pts

E ciency

15pts

Total:

100pts

Keep in mind that add functions are necessary to test other functions, so if an add doesn’t work, remove tests might fail as the items to be removed were not added correctly. Additionally, the size function is used many times throughout the tests, so if the size isn’t updated correctly or the method itself doesn’t work, many tests can fail.

A note on JUnits

We have provided a very basic set of tests for your code, in StacksQueuesStudentTests.java. These tests do not guarantee the correctness of your code (by any measure), nor does it guarantee you any grade. You may additionally post your own set of tests for others to use on the Georgia Tech GitHub as a gist. Do NOT post your tests on the public GitHub. There will be a link to the Georgia Tech GitHub as well as a list of JUnits other students have posted on the class Piazza (when it comes up).

If you need help on running JUnits, there is a guide, available on T-Square under Resources, to help you run JUnits on the command line or in IntelliJ.

Style and Formatting

It is important that your code is not only functional but is also written clearly and with good style. We will be checking your code against a style checker that we are providing. It is located in T-Square, under Resources, along with instructions on how to use it. We will take o a point for every style error that occurs. If you feel like what you wrote is in accordance with good style but still sets o the style checker please email Grayson Bianco (gbianco6@gatech.edu) with the subject header of \CheckStyle XML”.

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Homework 2: Stacks and Queues Due: See T-Square

Javadocs

Javadoc any helper methods you create in a style similar to the existing Javadocs. If a method is overridden or implemented from a superclass or an interface, you may use @Override instead of writing Javadocs. Any Javadocs you write must be useful and describe the contract, parameters, and return value of the method; random or useless javadocs added only to appease Checkstyle will lose points.

Exceptions

When throwing exceptions, you must include a message by passing in a String as a parameter. The mes-sage must be useful and tell the user what went wrong. \Error”, \BAD THING HAPPENED”, and \fail” are not good messages. The name of the exception itself is not a good message.

For example:

throw new PDFReadException(“Did not read PDF, will lose points.”);

throw new IllegalArgumentException(“Cannot insert null data into data structure.”);

Generics

If available, use the generic type of the class; do not use the raw type of the class. For example, use new ArrayList<Integer>() instead of new ArrayList(). Using the raw type of the class will result in a penalty.

Forbidden Statements

You may not use these in your code at any time in CS 1332.

break may only be used in switch-case statements

continue package

System.arraycopy() clone()

assert()

Arrays class Array class

Collections class

Collection.toArray()

Re ection APIs

Inner or nested classes

Debug print statements are ne, but nothing should be printed when we run your code. We expect clean runs – printing to the console when we’re grading will result in a penalty. If you submit these, we will take o points.

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Homework 2: Stacks and Queues Due: See T-Square

Provided

The following le(s) have been provided to you.

  1. ArrayQueue.java

This is the class in which you will implement the array-backed queue. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.

  1. ArrayStack.java

This is the class in which you will implement the array-backed stack. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.

  1. LinkedNode.java

This class represents a single node in the linked list. It encapsulates data and the next reference. Do not alter this le.

  1. LinkedQueue.java

This is the class in which you will implement the linked list-backed queue. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.

  1. LinkedStack.java

This is the class in which you will implement the linked list-backed stack. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.

  1. QueueInterface.java

This is one of the interfaces you will implement. All instructions for what the methods should do are in the javadocs. Do not alter this le.

  1. StackInterface.java

This is one of the interfaces you will implement. All instructions for what the methods should do are in the javadocs. Do not alter this le.

  1. StacksQueuesStudentTests.java

This is the test class that contains a set of tests covering the basic operations of your implementa-tions. It is not intended to be exhaustive and does not guarantee any type of grade. Write your own tests to ensure you cover all edge cases.

Deliverables

You must submit all of the following le(s). Please make sure the lename matches the lename(s) below. Be sure you receive the con rmation email from T-Square, and then download your uploaded les to a new folder, copy over the interfaces, recompile, and run. It is your responsibility to re-test your submission and discover editing oddities, upload issues, etc.

  1. ArrayQueue.java

  1. ArrayStack.java

  1. LinkedQueue.java

  1. LinkedStack.java

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