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Homework 8: Sorting
Homework 8: Sorting
Important There are general homework guidelines you must always follow. If you fail to follow any of the following guidelines you risk receiving a 0 for the entire assignment. 1. All submitted code must compile under JDK 8. This includes unused code, so don’t submit extra files that don’t compile. Any compile errors will result in a 0. 2. Do not include any package declarations in your classes. 3. Do not change any existing class headers, constructors, instance/global variables, or method signatures. 4. Do not add additional public methods. 5. Do not use anything that would trivialize the assignment. (e.g. don’t import/use java.util.ArrayList for an Array List assignment. Ask if you are unsure.) 6. Always be very conscious of efficiency. Even if your method is to be O(n), traversing the structure multiple times is considered inefficient unless that is absolutely required (and that case is extremely rare). 7. You must submit your source code, the .java files, not the compiled .class files. 8. After you submit your files, redownload them and run them to make sure they are what you intended to submit. You are responsible if you submit the wrong files. Sorting For this assignment you will be coding 6 different sorts: bubble sort, insertion sort, selection sort, quick sort, merge sort, and LSD radix sort. In addition to the requirements for each sort, we will be looking at the number of comparisons made between elements while grading. Your implementations must match what was taught in lecture and recitation to receive credit. Implementing a different sort or a different implementation for a sort will receive no credit even if it passes comparison checks. Comparator Each sorting method (except radix sort) will take in a comparator and use it to sort the elements of the array using various sorting algorithms described below and in the sorting file. You must use this comparator as the number of comparisons performed with it will be used when testing your assignment. Note that comparator.compare(x, y) is equivalent to x.compareTo(y). Inplace Sorts Some of the sorts below are inplace sorts. This means that the items in the array passed in aren’t copied over to another array or list. Note that you can still create variables that hold only one item; you cannot create another array or list in the method. Stable Sorts Some of the sorts below are stable sorts. This means that duplicates should remain in the same relative positions after sorting as they were before sorting. 1 Homework 8: Sorting Due: See T-Square Bubble Sort Bubble sort should be inplace and stable. It should have a worst case running time of O(n 2 ) and a best case running time of O(n). Insertion Sort Insertion sort should be inplace and stable. It should have a worst case running time of O(n 2 ) 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 first pass, index 0 and 1 should be considered as sorted. After the second pass, index 0-2 should be considered as sorted. After the third pass, index 0-3 should be considered as sorted, and so on. Selection Sort Selection sort should be inplace. It should have a worst case running time of O(n 2 ) and a best case running time of O(n 2 ). Quick Sort Quick sort should be inplace. It should have a worst case running time of O(n 2 ) and a best case running time of O(n log n). Merge Sort Merge sort should be stable. It should have a worst case running time of O(n log n) and a best case running time of O(n log n). Radix Sort Radix sort should be stable. 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 significant 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 us anything from the Math class besides Math.abs(). However, be wary of handling overflow if you use Math.abs()! 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: bubbleSort 10pts insertionSort 10pts selectionSort 10pts mergeSort 15pts quickSort 15pts lsdRadixSort 15pts Other: Checkstyle 10pts Efficiency 15pts Total: 100pts 2 Homework 8: Sorting Due: See T-Square A note on JUnits We have provided a very basic set of tests for your code, in SortingStudentTests.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. 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 off a point for every style error that occurs. If you feel like what you wrote is in accordance with good style but still sets off the style checker please email Raymond Ortiz (rortiz9@gatech.edu) with the subject header of “CheckStyle XML”. 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 message 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: Bad: throw new IndexOutOfBoundsException("Index is out of bounds."); Good: 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 LinkedList() 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. • break may only be used in switch-case statements • continue 3 Homework 8: Sorting Due: See T-Square • package • System.arraycopy() • clone() • assert() • Arrays class • Array class • Collections class • Collection.toArray() • Reflection APIs • Inner or nested classes • Lambda Expressions • Method References • Anything besides Math.abs() in the Math 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 files, just ask. Debug print statements are fine, 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 off points. Provided The following file(s) have been provided to you. 1. Sorting.java This is the class in which you will implement the different sorting algorithms. Feel free to add private static helper methods but do not add any new public methods, new classes, instance variables, or static variables. 2. SortingStudentTests.java This is the test class that contains a set of tests covering the basic operations on 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 file(s). Please make sure the filename matches the filename(s) below, and that only the following file(s) are present. T-Square does not delete files from old uploads; you must do this manually. Failure to do so may result in a penalty. After submitting, be sure you receive the confirmation email from T-Square, and then download your uploaded files 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. Sorting.java 4
Important There are general homework guidelines you must always follow. If you fail to follow any of the following guidelines you risk receiving a 0 for the entire assignment. 1. All submitted code must compile under JDK 8. This includes unused code, so don’t submit extra files that don’t compile. Any compile errors will result in a 0. 2. Do not include any package declarations in your classes. 3. Do not change any existing class headers, constructors, instance/global variables, or method signatures. 4. Do not add additional public methods. 5. Do not use anything that would trivialize the assignment. (e.g. don’t import/use java.util.ArrayList for an Array List assignment. Ask if you are unsure.) 6. Always be very conscious of efficiency. Even if your method is to be O(n), traversing the structure multiple times is considered inefficient unless that is absolutely required (and that case is extremely rare). 7. You must submit your source code, the .java files, not the compiled .class files. 8. After you submit your files, redownload them and run them to make sure they are what you intended to submit. You are responsible if you submit the wrong files. Sorting For this assignment you will be coding 6 different sorts: bubble sort, insertion sort, selection sort, quick sort, merge sort, and LSD radix sort. In addition to the requirements for each sort, we will be looking at the number of comparisons made between elements while grading. Your implementations must match what was taught in lecture and recitation to receive credit. Implementing a different sort or a different implementation for a sort will receive no credit even if it passes comparison checks. Comparator Each sorting method (except radix sort) will take in a comparator and use it to sort the elements of the array using various sorting algorithms described below and in the sorting file. You must use this comparator as the number of comparisons performed with it will be used when testing your assignment. Note that comparator.compare(x, y) is equivalent to x.compareTo(y). Inplace Sorts Some of the sorts below are inplace sorts. This means that the items in the array passed in aren’t copied over to another array or list. Note that you can still create variables that hold only one item; you cannot create another array or list in the method. Stable Sorts Some of the sorts below are stable sorts. This means that duplicates should remain in the same relative positions after sorting as they were before sorting. 1 Homework 8: Sorting Due: See T-Square Bubble Sort Bubble sort should be inplace and stable. It should have a worst case running time of O(n 2 ) and a best case running time of O(n). Insertion Sort Insertion sort should be inplace and stable. It should have a worst case running time of O(n 2 ) 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 first pass, index 0 and 1 should be considered as sorted. After the second pass, index 0-2 should be considered as sorted. After the third pass, index 0-3 should be considered as sorted, and so on. Selection Sort Selection sort should be inplace. It should have a worst case running time of O(n 2 ) and a best case running time of O(n 2 ). Quick Sort Quick sort should be inplace. It should have a worst case running time of O(n 2 ) and a best case running time of O(n log n). Merge Sort Merge sort should be stable. It should have a worst case running time of O(n log n) and a best case running time of O(n log n). Radix Sort Radix sort should be stable. 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 significant 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 us anything from the Math class besides Math.abs(). However, be wary of handling overflow if you use Math.abs()! 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: bubbleSort 10pts insertionSort 10pts selectionSort 10pts mergeSort 15pts quickSort 15pts lsdRadixSort 15pts Other: Checkstyle 10pts Efficiency 15pts Total: 100pts 2 Homework 8: Sorting Due: See T-Square A note on JUnits We have provided a very basic set of tests for your code, in SortingStudentTests.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. 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 off a point for every style error that occurs. If you feel like what you wrote is in accordance with good style but still sets off the style checker please email Raymond Ortiz (rortiz9@gatech.edu) with the subject header of “CheckStyle XML”. 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 message 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: Bad: throw new IndexOutOfBoundsException("Index is out of bounds."); Good: 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 LinkedList() 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. • break may only be used in switch-case statements • continue 3 Homework 8: Sorting Due: See T-Square • package • System.arraycopy() • clone() • assert() • Arrays class • Array class • Collections class • Collection.toArray() • Reflection APIs • Inner or nested classes • Lambda Expressions • Method References • Anything besides Math.abs() in the Math 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 files, just ask. Debug print statements are fine, 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 off points. Provided The following file(s) have been provided to you. 1. Sorting.java This is the class in which you will implement the different sorting algorithms. Feel free to add private static helper methods but do not add any new public methods, new classes, instance variables, or static variables. 2. SortingStudentTests.java This is the test class that contains a set of tests covering the basic operations on 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 file(s). Please make sure the filename matches the filename(s) below, and that only the following file(s) are present. T-Square does not delete files from old uploads; you must do this manually. Failure to do so may result in a penalty. After submitting, be sure you receive the confirmation email from T-Square, and then download your uploaded files 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. Sorting.java 4
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