ASSIGNMENT 2 Loops, loops, and more loops! COMP-202B, Winter

QUESTION

http://www.cs.mcgill.ca/~cs202/2013-01/web/assignments.htmlASSIGNMENT 2Loops, loops, and more loops!COMP-202B, Winter 2013, All SectionsDue: February 25th, 2013 (23:30)Please read the entire pdf before starting.You must do this assignment individually and, unless otherwise specified, you must follow all the generalinstructions and regulations for assignments. Graders have the discretion to deduct up to 10% of the valueof this assignment for deviations from the general instructions and regulations. These regulations are postedon the course website. Be sure to read them before starting.PartPartPartPart1:2a, Question 1:2a, Question 2:2b, Question 1:0 points50 points15 points35 points100 points totalIt is very important that you follow the directions as closely as possible. The directions, whileperhaps tedious, are designed to make it as easy as possible for the TAs to mark the assignments by lettingthem run your assignment through automated tests. While these tests will not determine your entire grade,it will speed up the process significantly, which will allow the TAs to provide better feedback and not wastetime on administrative details. Plus, if the TA is in a good mood while he or she is grading, then thatincreases the chance of them giving out partial marks :)Part 1 (0 points): Warm-upDo NOT submit this part, as it will not be graded. However, doing these exercises might help you to dothe second part of the assignment, which will be graded. If you have difficulties with the questions of Part1, then we suggest that you consult the TAs or instructors during their office hours; they can help you andwork with you through the warm-up questions.Some of these questions we haven’t yet gotten to in class as they rely on loops. The notes for loops areposted currently and the notes for arrays will be posted shortly.Warm-up Question 1 (0 points)Write a method printTypeOfChar. This method should take as input a char and print the following.If the char is upper case, your method should print UPPERCASE. If the char is lower case, your methodshould print LOWERCASE. If the char is a numerical digit, your method should print NUMBER. If the char isany other symbol, your method should print SYMBOL. Note that it is not necessary to make 52 differentcases if you consider the order of the Unicode chart and the fact that you can use the < and > operatorson them.Warm-up Question 2 (0 points)Write a method countUppercase. Your method should take as input a String and return an int1representing the number of upper case letters in the String. Now add a main method where you usethe Scanner class to read a String from the user and call your method, outputting the returned result.To access a character within a String named foo at a given position, you can write foo.charAt(intexpression) where int expression is any expression that evaluates to an int. Note that the first symbolof a String is at position 0.String words = "howdy";char c = words.charAt(0); //c is now ’h’char d = words.charAt(2 + 1); //d is now ’d’char e = words.charAt(5); // error: program crashes because no such value//since the counting starts from 0, the last letter is actually at position 4.char f = words.charAt(words.length()); // same problem at charAt(5) aboveWarm-up Question 3 (0 points)A prime number is a positive number whose only even divisors are 1 and itself. Write a method isPrimethat takes as input an integer n and returns a boolean representing whether n is prime or not. Makesure to handle cases where the integer is negative. (Your method should return false in these cases.)Warm-up Question 4 (0 points)x is a factor of y if y is a multiple of x. Write a method calculateFactorsSum. The method shouldtake as input an int n and return an int representing the sum of the factors of the number n.Warm-up Question 5 (0 points)x is a factor of y if y is a multiple of x. Write a method calculateFactors. The method should takeas input an int n and return an int containing all the factors of the number n.Warm-up Question 6 (0 points)Rewrite your question from the assignment 1 so that you can calculate the inverse of any student IDinstead of just a 4 digit student id. Put this code inside a method called reverseDigit. Note that tostore a large number you will want to use the type long instead of int.Warm-up Question 7 (0 points)Write a method lengthOfVector that takes as input an int vector and returns a double calculatedby first squaring all the terms in vector, then calculating the sum of this and finally taking the squareroot of the sum.Warm-up Question 8 (0 points)Write a method dotProduct which takes as input two int and calculates the dot product of thesetwo arrays. (Remember you can take the dot product of 2 vectors by multiplying each coordinate bythe corresponding element and then summing the results.)Part 2The questions in this part of the assignment will be graded.We have provided you with code that will AID you in testing your code. This is not meant as a substitutefor testing the code on your own!Your code must at least compile with the test cases. If your code compiles with the test cases butdoes not pass all the test cases, you will lose some points on the question, but it will be penalized as in othermistakes–that is, you’ll lose a few points for the specific cases it fails, but that will be all. However, you’lllose significant points if it does not compile with the test cases since in this case your code would not havepassed any test cases. The reason for this requirement is the test cases will make things much easier for theTAs to grade. If your code doesn’t even run with the test cases then it is difficult to grade. If you arehaving trouble getting your code to compile with the test cases, please see an instructor or aTA and they will help you!Page 2You should not use Scanner or have print statements in any of the required methods with theexception of System.out.println statements being allowed inside of the main method of part2a. It is recommended that you add print statements temporarily to help you debug your program whenyou get the wrong result, but you should remove these before handing the assignment in. You may chooseto put Scanner into your ungraded main method for the second question if you like, but another potentiallyfaster option is to hard code the numbers into your main method. If you are finding yourself puttingScanner into the methods other than main, please see a TA or instructor for help and reviewthe notes on method calling.Part 2a: Approximating sin(x)The following question should be put into a class called TaylorSin.The Math library contains a method that allows you to calculate the trigonometric function sin(x). You canexecute this method by writing Math.sin(e) for some expression e of type double. In this question, you willinitially pretend that this method does NOT exist and write your own approximation of sin(x) that doesnot use any library methods. Then, to check your work at the end, you will call M ath.sin(x) and comparethe results.Methodology: Due to properties of something called a Maclaurin series or Taylor series, you can approximate the function sin(x) using the following formula:asin(x) ≈(−1)nn=0x3x5x7x(2a+1)x(2n+1)=x−+−+ …(2n + 1)!3!5!7!(2a + 1)!where a is chosen to be a large number. We will use this formula to approximate sin(x).Question 1: Writing the sin(x) method (50 points)Write a method called sin that takes as input a double and returns a double. Your method shouldapproximate sin(x) using the above formula by setting the value of a to be a class constant with value10. You may not use any library method (such as Math.pow) for this. You must use at least one loopin your method.Hint: If you are having trouble figuring out how to get started, start by making a smaller version ofthis problem and creating a method out of it. In this case, you are asked to take the sum of manyterms. A simpler version of the question would be to calculate just one term. You could write a methodcalculateTerm that took as input a double x and an int n and returned the nth term in the sequence.After you write this method, test it, by calling it from the main method and verify that it works. Tocalculate the sum, you can then call your method several times. Note that the method calculateTermmight be further divided. (For example, you may want to write a method for calculating power orfactorial.)Note: The approximation will only be close to the actual value with a=10 for small valuesof x (between -1 and 1). For larger values, you would need to increase a. However, this isnot required for the assignment. Doing so in fact may cause numerical computation errorsrelated to overflow.Question 2: Checking your sin(x) method (15 points)In order to test your sin(x) method, you will do an experiment. To perform this experiment you shoulddo the following.Write a main method in which you produce a table comparing, for every value of x from-1 to 1 in increments of .01, the values of x, Math.sin(x), sin(x) (your version) and theabsolute value of the difference between the value returned by Math.sin and your version.Page 3The first column of your results should be x, the 2nd column should be Math.sin(x), the third columnshould be your results, and the 4th column the absolute value of the difference. (The idea is we areassuming that Math.sin(x) returns the correct value so if our results match it, then we must have codedsin(x) correctly)A sample run of the program and what your output should be is posted on the course webpage with thefile name SampleRunSin.txt. Your numbers may differ slightly due to rounding issues. (Notice that inthe sample output there are several rounding issues where the results don’t show up ”perfectly” in thex column for example. This is fine.)Part 2b: Writing an automated plagiarism detector!In this question, you will write code that compares two Strings and looks for similarities. This would beused to detect cheating. A sample main method is provided for you inside the file PlagiarismDetector.javadownloadable on the course webpage which you may use if you like or change as you desire. However, yourmain method for this question will not be graded and should be used simply for testing. The provide codewill ask the user for the 2 files to read from and load them into Strings. Note that in order for it to work,these two files must be inside the same folder as your .class file. If you are using eclipse you may need tomanually find the .class file and copy the .txt files into that folder. The program will only work on .txt files(not .doc or .pdf for example).You should write the following method:Question 1: Plagiarism Detection (35 points)Write a method compareStrings which takes as input two String and returns a boolean representingwhether your program concludes that the two strings are very similar to each other. A boolean resultof true indicates the Strings are very close to each other and false indicates otherwise. Your methodshould determine this is based on the following rule:If at least 90% of the words in the first String appear in the second String AND at least90% of the words in the second String appear in the first String, your method shouldreturn true. Otherwise your method should return false.For the purpose of this assignment, a “word” is any sequence of characters other than newlines, tabs,spaces, and other “white space” characters. For example the String ”abc d3; 33” is considered to have3 words: abc, d3;, and 33. You should perform the check in a case sensitive fashion meaning that thewords hello and HELLO will be treated as different words.Important hint: There is a library method defined on all Strings which allows you to produce a Stringbased on a delimiter by splitting the String into several pieces. To split a String into several piecesbased on “whitespace” (new lines, tabs, space, etc), you can call split in the following way. Assume theString you want to split is called foo.String pieces = foo.split("s");For example, if foo contains the contents a bc def
ghi then writing foo.split("s") will producea String with the contents a, bc, def, and ghi (remember that
is the code for storing a new linein a char or String). Note that the double backslash is necessary (as opposed to just one backslash)because the method split is supposed to take as input a String of length 2, with the first character beinga backslash. Since backslash denotes special characters, a backslash itself is a special character!Here are a few examples along with the expected results:• ”a3 bb cc dd” vs ”bb cc dd a3” yields True• ”aa bb cc” vs ”aa aa aa” yields False because only 1 of 3 of the words from the second String arein the firstPage 4• ”a b c d e f g h i j a a a a a a” vs ”a b c d e f g h i k” yields True since at least 90 percent of thewords from each String are included in the other.• ”a a a a a a a a a a a a b” vs ”b b b b b b b b b b a” yields True because at least 90 percent of thewords from each String are included in the other. Even though a appears multiple times in thefirst String the checker will only check that each at least 90 percent of the letters in one Stringoccur in the other. The Strings ”a” and ”b” both appear in both Strings and so it is a match.• ”a a a a a a a a a b c” vs ”a c” yields True since there are 11 words in the first String. The 9 as10are all found in the second String, the b is not and the c is. So 11 of the words in the first Stringoccur in the second. (The reverse match is trivially true since all words in the second String occurin the first.)Note finally that you may make the following two assumptions: (That is, you do NOT need to handlethese cases)• Neither of the String variables passed as input will be null• Neither Strings will have consecutive white space characters. That is, you do not need to handlecases with 2 spaces in a row for example.Verifying your codeRun your code against the test programs to verify it. To do this, you should make sure that TaylorSin.java,PlagiarismDetector.java, and AssignmentTwoTests.java are all in the same folder.Then, compile all of them together by typingjavac *.javaORjavac AssignmentTwoTests.java PlagiarismDetector.java TaylorSin.javaIn Eclipse, Dr. Java, or the command prompt, you should make sure that the four files are inside the samefolder.If the program does not compile, it means you are either missing a public method or one of the requiredpublic methods does not take the correct arguments. Your code must compile with these test cases. If youare not able to do so, you should ask a TA or instructor for help. After this, you may run the test programby typingjava AssignmentTwoTestsAs you are writing your code, you may want to test things immediately rather than waiting until you’vefinished the assignment. In this case, a good thing to do is write the method headers and “skeleton methods”with simple return expressions for the required methods. The test cases for the methods for which you haveonly skeletons will still fail in most cases, but you’ll be able to run the test cases on the working ones.What To SubmitYou should submit your assignment on MyCourses. In order to do this, you will need to make a zip of thefile. You can do this on windows by following the instructions at this link: http://condor.depaul.edu/slytinen/instructions/zip.html. On a mac or linux, you can find instructions at http://osxdaily.com/2012/01/10/how-to-zip-files-in-mac-os-x/You should submit a zip file called Assignment2.zip with the following files inside of it.Page 5TaylorSin.javaPlagiarismDetector.javaConfession.txt (optional) In this file, you can tell the TA about any issues you ran into doingthis assignment. If you point out an error that you know occurs in your problem, it may leadthe TA to give you more partial credit. On the other hand, it also may lead the TA to noticesomething that otherwise he or she would not.Page 6

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