Description
Style and Formatting
It is important that your code is not only functional, but written clearly and with good programming style. Your code will be checked against a style checker. The style checker is provided to you, and is
located on Canvas. It can be found under Files, along with instructions on how to use it. A point is deducted for every style error that occurs. If there is a discrepancy between what you wrote in accordance with good style and the style checker, then address your concerns with the Head TA.
Javadocs
Write javadoc comments for any helper methods you create in a style similar to the existing 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.
Vulgar/Obscene Language
Any submission that contains profanity, vulgar, or obscene language will receive an automatic zero on the assignment. This policy applies not only to comments/javadocs, but also things like variable names.
Exceptions
When throwing exceptions, you must include a message by passing in a String as a parameter. The message must be useful and tell the user what went wrong. \Error”, \BAD THING HAP-PENED”, and \fail” are not good messages. The name of the exception itself is not a good message. For example:
Bad: throw new IndexOutOfBoundsException(‘‘Index is out of bounds.’’);
Good: throw new IllegalArgumentException(‘‘Cannot insert null data into data structure.’’); In addition, you may not use try catch blocks to catch an exception unless you catching an exception you have explicitly thrown yourself with the throw new ExceptionName(‘‘Exception Message’’); syn-
tax (replacing ExceptionName and Exception Message with the actual exception name and message respectively).
Generics
If available, use the generic type of the class; do not use the raw type of the class. For example, use new LinkedList<Integer>() instead of new LinkedList(). 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.
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package
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System.arraycopy()
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clone()
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assert()
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Arrays class
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Array class
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Thread class
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Collections class
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Collection.toArray()
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Re ection APIs
Homework 6: Sorting Due: See Canvas
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Inner or nested classes
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Lambda Expressions
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Method References (using the :: operator to obtain a reference to a method)
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Anything besides Math.abs() in the Math class (for this homework only)
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String class (for this homework only)
If you’re not sure on whether you can use something, and it’s not mentioned here or anywhere else in the homework les, just ask.
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.
JUnits
We have provided a very basic set of tests for your code. These tests do not guarantee the correctness of your code (by any measure), nor do they 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.
If you need help on running JUnits, there is a guide, available on Canvas under Files, to help you run JUnits on the command line or in IntelliJ.
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Homework 6: Sorting Due: See Canvas
Sorting
For this assignment you will be coding 3 di erent sorts: insertion sort, merge sort, and LSD radix sort. You will also be coding the kth select algorithm that is very similar to the quick sort algorithm. In addition to the requirements for each sort (except LSD radix sort), to test for e ciency, we will be looking at the number of comparisons made between elements while grading.
For each of the sorting algorithms, you may assume that the arrays you are sorting will not contain null elements. You should also assume that arrays may contain any number of duplicate elements.
Your implementations must match what was taught in lecture and recitation to receive credit. Implementing a di erent sort or a di erent implementation for a sort will receive no credit even if it passes comparison checks.
Comparator
Each method (except LSD radix sort) will take in a Comparator and use it to compare the elements of the array in various algorithms described below and in the sorting le. You must use this Comparator as the number of comparisons performed with it will be used when testing your assignment. See the Java API for details about how the Comparator works and the meaning of the returned value.
Generic Methods
Most of the assignments for this class so far have utilized generics by incorporating them into the class declaration. However, the rest of the assignments will have you implement various algorithms as static methods in a utility class. Thus, the generics from here on will use generic methods instead of generic classes (hence the <T> in each of the method headers and javadocs). This also means any helper methods you create will also need to be static with the same <T> in the method header.
In-Place Sorts
Some of the sorts below are in-place sorts. This means that the items in the array passed in should not get copied over to another data structure. Note that you can still create variables that hold only one item; you cannot create another data structure such as an array or list in the method.
Stable Sorts
Some of the sorts below are stable sorts. This means that duplicates must remain in the same relative positions after sorting as they were before sorting.
Adaptive Sorts
Some of the sorts below are adaptive sorts. This means that the algorithm takes advantage of existing order in the input array. The algorithm can detect existing order in the input array and optimize its performance based on that order.
Insertion Sort
Insertion sort should be in-place, stable, and adaptive. It should have a worst case running time of O(n2) and a best case running time of O(n).
Note that, for this implementation, you should sort from the beginning of the array. This means that after the rst pass, indices 0 and 1 should be relatively sorted. After the second pass, indices 0-2 should be relatively sorted. After the third pass, indices 0-3 should be relatively sorted, and so on.
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Homework 6: Sorting Due: See Canvas
Merge Sort
Merge sort should be out-of-place, stable, and not adaptive. It should have a worst case running time of O(nlogn) and a best case running time of O(nlogn). When splitting an odd size array, the extra data should go on the right.
LSD Radix Sort
LSD Radix sort should be out-of-place, stable, and not adaptive. It should have a worst case running time of O(kn) and a best case running time of O(kn), where k is the number of digits in the longest number. You will be implementing the least signi cant digit version of the sort. You will be sorting ints. Note that you CANNOT change the ints into Strings at any point in the sort for this exercise. The sort must be done in base 10. Also, as per the forbidden statements section, you cannot use anything from the Math class besides Math.abs(). However, be wary of handling over ow if you use Math.abs()!
Kth Select
Kth select should be inplace. It should have a worst case running time of O(n2) and a best case running time of O(n). Your implementation must be randomized as speci ed in the method’s javadocs. Logically, it is similar to a one-sided quick sort. When asked for the kth smallest, you should return what would be at index k 1 if the array was perfectly sorted.
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Homework 6: Sorting Due: See Canvas
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.
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Methods: |
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insertionSort |
10pts |
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mergeSort |
25pts |
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lsdRadixSort |
15pts |
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kthSelect |
25pts |
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Other: |
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Checkstyle |
10pts |
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E ciency |
15pts |
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Total: |
100pts |
Provided
The following le(s) have been provided to you. There are several, but we’ve noted the ones to edit.
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Sorting.java
This is the class in which you will implement the di erent sorting algorithms. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.
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SortingStudentTests.java
This is the test class that contains a set of tests covering the basic algorithms in the Sorting class. 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) to Gradescope. Make sure all le(s) listed below are in each submission, as only the last submission will be graded. Make sure the lename(s) matches the lename(s) below, and that only the following le(s) are present. If you resubmit, be sure only one copy of each le is present in the submission. If there are multiple les, do not zip up the les before submitting; submit them all as separate les.
Once submitted, double check that it has uploaded properly on Gradescope. To do this, download your uploaded le(s) to a new folder, copy over the support le(s), recompile, and run. It is your sole responsibility to re-test your submission and discover editing oddities, upload issues, etc.
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Sorting.java
