Problem Set Five. A. Pencil-and-Paper Exercises (44 points total) [1] 12 points (2 points for each part) use file Prob01.txt

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1 Computer Science 1: Great Ideas in Computer Science Handout #12 Problem Set Five This assignment is designed to reinforce your comprehension of methods that manipulate Strings and other types of objects particularly arrays. Many of you will find Chapters 7 and 8 in the Reges textbook to be appropriate background reading before working on this problem set. Note that for 3 of the programming problems, you may pair up with one other CS-1 student. If you don t know anyone in the class but would like to work with someone, send to cs1@fas.harvard.edu and we will help find you a partner. Unless otherwise indicated, everything that the human would type to the computer has been underlined. Everything that the computer types is not. Electronic submission is due prior to 5 PM on Friday afternoon, April 8. Use the Unix command cs1submit ps5 (assuming you have created a folder in your cs1 directory named ps5 that contains your solutions). A. Pencil-and-Paper Exercises (44 points total) (your responses to each question in this part should appear in text files) [1] 12 points (2 points for each part) use file Prob01.txt Suppose a program contains the declaration String s = "Java, Java, Java ; Now evaluate each of the following independent expressions. If you can t remember how some of these String methods work, try looking at the documentation at download.oracle.com/javase/7/docs/api/ (a) (b) s.substring(0,4) == Java" s.lastindexof ( av") (c) s.indexof ( a, 5) (d) (e) s.indexof ( av", s.length()-10) s.substring(s.lastindexof (s.charat(5))) (f) s.substring (2, s.length()-3) Spring, 2016 Dr. H. H. Leitner

2 Computer Science 1: Great Ideas in Computer Science Page!2 [2] 4 points use file Prob02.txt The following simple program, which is supposed to create a 20-element array variable named cs1 that it fills with random integer values, contains a number of errors. Some of the blunders will cause an error message at compilation time, while others may cause an error at execution time. Find (and fix) all of them! class Foobar { public static void main (String [] args) { double [20] cs1; for (int i = 0; i <= cs1.length(); i++) cs1[i] = Math.random * 100; } } [3] 12 points (3 points for each part) use file Prob03.txt Write Java variable declarations to create new array objects of the following types. Note that you do NOT need to initialize any of them with specific values. (a) (b) (c) (d) a single-dimensioned array named a with the answers to 20 true/false quiz questions a single-dimensioned array named b that contains the average family size in the years 1900, 1920, 1940, 2010 a 2D array named c that contains the total number of inches of rainfall for a city in each of twelve months, recorded over a period of 5 years. a single-dimensioned array named d that contains the 4 candidates in some presidential primary election. You should define a Candidate class with private instance variables for the person s name and the number of votes received. Define a single Candidate constructor that accepts a candidate s name and number of votes. Do not bother defining any setters, getters or other instance methods.

3 ! Computer Science 1: Great Ideas in Computer Science Page!3 [4] 12 points (3 points for each part) use file Prob04.txt Suppose that final integer SIZE has been properly declared and initialized, and that an array named sample has been declared as follows: int [] sample = new int [SIZE]; Write one or more Java statements to perform the following. Note that each task is independent of the other three: (a) Initialize all array elements to the value 5. (b) (c) (d) Swap the first value in the array with the last value in the array Change any negative values to positive values (of the same magnitude) Print the contents of the odd-numbered locations in the arra [5] 4 points use file Prob05.txt Tic-tac-toe is a simple game in which each square in a 3 x 3 grid contains the letter X, the letter O or a blank space, as in the following: Write a single Java statement that constructs a two-dimensional array of char values (named tictactoe) and initializes it to the above configuration. Use nested initializers, as described in lecture.

4 Computer Science 1: Great Ideas in Computer Science Page!4 B. Programming Problems (125 points total) [6] 15 points use file Sentence.java Write a complete Java program that reads a line of input from the keyboard (using the nextline() Scanner method) and outputs either declarative, exclamatory, or interrogative according to whether the last character on the line was a period, an exclamation mark, or a question mark!!?!. Your program should output the message bad ending if the last character is none of these punctuation marks. [7] 20 points use file Vowels.java Define a method named vowelcount that accepts a String as its only parameter, and constructs (and returns) an array of integers that represents the counts of each vowel in the String. The array returned by your method should hold precisely 5 integers: the first is the count of A s, the second is the count of E s, the third is the count of I s, the fourth is O s, and the fifth is U s. For example, the call vowelcount ( I think, therefore I am ) should return an array containing the values [1, 3, 3, 1, 0]. Write a main program that thoroughly tests out vowelcount.

5 Computer Science 1: Great Ideas in Computer Science Page!5 [8] 25 points use file Duplication.java This problem may be worked on with one other CS1 student. If you decide to collaborate with another student, indicate the name of your helper as a comment inside the Duplication.java file. A common problem is to receive a list of values (e.g., addresses) that contain duplicates. Write a Java method named removeduplicates that accepts one argument, an array of String values, and returns a new array that has no duplicate values. The original array should not get reordered. For example, the code String [] values = {"A", "C", "C", "B", "A", "C", "B", "B", "A"}; String [] newlist = removeduplicates (values); for (int i = 0; i < newlist.length; i++) { System.out.print (values[i] + " "); } System.out.println(); should output A C B Write a main method that convincingly demonstrates your method in action. [9] 20 points modify files Rational.java and RatTest.java For the Rational class described in lecture, define a method named lessthanrat so that two rational numbers can be compared to determine if the first one is arithmetically less than the second one. For example, the expression a.lessthanrat(b) is true, given Rational a = new Rational (8, 16); Rational b = new Rational (2, 3); Be sure to copy the Rational.java file from the ~cs1/java directory to your own account in order to test out your solution. You can also copy the RatTest.java file, and modify it in order to test your lessthanrat method.

6 Computer Science 1: Great Ideas in Computer Science Page!6 [10] 20 points use files Pizza.java and PizzaParty.java This problem also may be worked on with one other CS1 student. If you decide to do so, indicate the name of your helper as a comment inside the PizzaParty file. Pizzas can be ordered in several sizes. Some pizza parlors cut all pizzas into 8 slices, while others get more slices out of the larger pizza pies. It might be useful to know what size pie offers the best deal in terms of cost per slice or cost per square inch of pizza. Here s a Java program to help determine these facts: public class PizzaParty { public static void main(string[] args) { Pizza appetizer = new Pizza ("Pepperoni", 16, 10.50, 10); Pizza maincourse = new Pizza ("Anchovy & Pineapple, 20, 11.95, 8); printpizzastats (appetizer); System.out.println(); printpizzastats (maincourse); } } public static void printpizzastats (Pizza p) { System.out.printf ("Your %s pizza has %.2f square inches " + " per slice.\n", p.getname(), p.areaperslice()); System.out.printf ("One slice costs $%.2f, which comes + " to $%.3f per square inch.\n", p.costperslice(), p.costpersquareinch() ); }

7 Computer Science 1: Great Ideas in Computer Science Page!7 Your task is to implement the Pizza class with instance variables and methods Note that the Pizza constructor accepts 4 parameters: the first is the name of the pizza, the second argument is the radius of the pizza, the third argument is the total price of the pizza, and the fourth argument is the number of slices this pizza will be cut into. Please include the PizzaParty class with your submission. If the Pizza class gets properly defined, here is what your program should look like in action (note the use of printf to format the output of double values in an appropriate way). Your Pepperoni pizza has square inches per slice. One slice costs $1.05, which comes to $0.052 per square inch. Your Anchovy & Pepper pizza has square inches per slice. One slice costs $1.49, which comes to $0.038 per square inch. [11] 25 points use file PigLatin.java Write a method named piggie that accepts a String argument containing a single English language word, and returns the Pig Latin equivalent. Pig Latin is English, but with the initial consonant sound moved to the end of the word, followed by ay. However, words that begin with vowels simply have way appended to the end of the word. For example, the input deepest gets translated into eepest-day shade gets translated to ade-shay Obama gets translated to Obama-way, and you gets translated to ou-yay queen gets translated to een-quay (note the u stays with q ) by gets translated to y-bay (note that y is a vowel) Write a main method that tests your program out by asking the user to input a complete line of text (basically an English sentence) and then outputs the equivalent in Pig Latin by calling on your piggie method repeatedly (once for each word in the sentence). Consider using the next() and hasnext() methods of the Scanner class to simplify the programming.

8 Computer Science 1: Great Ideas in Computer Science Page!8 C. Additional Problems (up to 45 points) You must turn in a solution to any one of the following problems. For extra credit, you may turn in a solution to at most any two additional problems (in other words, one or two problems IN ADDITION to the required problem). Indicate which problems are for extra credit. [12] 15 points use file RepeatedDigits.java Write a Java program that allows the user to input an integer value; after this number is entered, your program will print out how many times each of the digits from 0 through 9 appeared in your input value. Here is how your program might appear in action: Please enter an integer: Digit: Occurrences: Note that leading zeros should be ignored; negative numbers can be considered valid input by somehow ignoring the - sign. The occurrences should be stored in a single array. [13] 15 points use file ArrayIntersect.java Write a Java method named intersection that accepts two arguments, both arrays of integers; these arrays may contain a different number of elements from each other. Your method must return the value true if there exists an integer value, k, that is contained in both tables. If no such integer exists, then your method should return the value false. You are not to assume that k is any integer value in particular! Write a main() method that convincingly demonstrates the features of your method.

9 Computer Science 1: Great Ideas in Computer Science Page!9 [14] 15 points use file MagicSquare.java A magic square is an n x n grid of the integers 1 through n 2 that sum to the same value across rows, down columns, and along the two diagonals. An example is! Note how every row, column and diagonal in this 3 x 3 grid sums to the value 15. An old method for constructing magic squares of an odd order was devised by the mathematician de la Loubére. It involves placing the next number of the magic square DIAGONALLY UP AND TO THE RIGHT OF THE PREVIOUS NUMBER, with the following caveats: One row up from the top row lands you in the bottom row. One column right from the rightmost column lands you in the leftmost column. If the desired cell is already occupied, then instead place the next number below the previous one. Begin the whole process by placing the number 1 in the middle of the top row. Write a complete Java program to read an odd integer input from the keyboard, and then display a magic square of that order using the ideas presented above.

10 Computer Science 1: Great Ideas in Computer Science Page!10 [15] 15 points use file Roman.java Write a program to read in a string of characters that represent a Roman numeral and then convert it to Arabic form (an integer). The character values for Roman numerals are as follows: Roman Symbol Value M 1000 D 500 C 100 L 50 X 10 V 5 I 1 Test your program with the following data: LXXXVII (87), CCXIX (219), MCCCLIV (1354), MMDCLXXIII (2673) and MCDLXXVI (1476). If you don t know (or can t remember) how Roman numerals work, Google it! [16] 15 points use file MindtheGap.java Write a static method named mingap that takes an integer array as a parameter and that returns the minimum gap between adjacent values in the array. The gap between two adjacent values in a list is defined as the second value minus the first value. For example, suppose a variable called "list" is an array of integers that stores the following sequence of values: {1, 3, 6, 7, 12} The first gap is 2 (3-1), the second gap is 3 (6-3), the third gap is 1 (7-6) and the fourth gap is 5 (12-7). Thus, the call mingap (list) should return 1 because that is the smallest gap in the list. Notice that the minimum gap could

11 Computer Science 1: Great Ideas in Computer Science Page!11 be a negative number. For example, if list stores the following sequence of values {3, 5, 11, 4, 8} then the gaps would be computed as 2 (5-3), 6 (11-5), -7 (4-11), and 4 (8-4). Of these values, -7 is the smallest, so it would be returned. By the way, this gap information can be helpful for determining other properties of the list. For example, if the minimum gap is greater than or equal to 0, then you know the list is in sorted (nondecreasing) order. (Do you understand why?) If the gap is greater than 0, then you know the list is both sorted and contains unique values (i.e., it is strictly increasing). If your method is passed an array with fewer than 2 elements, mingap should return 0. But sure to convincingly test your method out on a variety of arrays using a main program of your own design. [17] 15 points use files TicTacToe.java and TicTacToeBoard.java Write a program that allows two people to play a game of tic-tac-toe, with the computer acting as a referee. Here is what your program might look like in action: Welcome! Tic-Tac-Toe is a two player game. Enter player one's name: Foo Enter player two's name: Bar Players take turns marking a square. Only squares not already marked can be picked. Once a player has marked three squares in a row, he or she wins! If all squares are marked and no three squares are the same, a tied game is declared. Have Fun! Game board: It is Foo's turn. Pick a row between 1 and 3: 1 Pick a column between 1 and 3: 1 Game board:

12 Computer Science 1: Great Ideas in Computer Science Page!12 X It is Bar's turn. Pick a row between 1 and 3: 2 Pick a column between 1 and 3: 2 Game board: X O It is Foo's turn. Pick a row between 1 and 3: 2 Pick a column between 1 and 3: 2 ILLEGAL CHOICE! TRY AGAIN... Pick a row between 1 and 3: 2 Pick a column between 1 and 3: 1 Game board: X X O It is Bar's turn. Pick a row between 1 and 3: 3 Pick a column between 1 and 3: 1 Game board: X X O O It is Foo's turn. Pick a row between 1 and 3: 3 Pick a column between 1 and 3: 3 Game board: X X O O X It is Bar's turn. Pick a row between 1 and 3: 1 Pick a column between 1 and 3: 3

13 Computer Science 1: Great Ideas in Computer Science Page!13 Game board: X O X O O X Game Over - Bar WINS!!! In solving this problem, create a TicTacToeBoard class that contains a two- dimensional array representing the current state of a tic-tac-toe board. Initially, every element of this array could contain a space character, to indicate it is empty. Your TicTacToeBoard class should only have private variables and these and only these public methods: // constructor public TicTacToeBoard() { } // returns a string representation of the board public String tostring() { } // tries to play c (X or O) at row, col // returns true if square was legal and not occupied public boolean makemove (int row, int col, char c) { } // returns true if the board is a win for either X or O public boolean iswin() { } Your tostring method in this class will make it possible for the TicTacToe client program to print the board as shown in the above output. Your main program will alternately let each of the two players make a move, but not allow any move that is illegal either because a particular square is already occupied, or because a value less than 1 or greater than 3 has been input for the row or column position. After each turn is made the computer should check if any row, column or diagonal contains three X marks or three O marks; if so, a winner should be declared and the game should end at that point. If nobody has won after 9 moves, a tie should be declared.

14 Computer Science 1: Great Ideas in Computer Science Page!14 [18] 15 points use file CardinalOrdinal.java And this problem may also be worked on with one other CS1 student. If you decide to do so, indicate the name of your helper as a comment inside the CardinalOrdinal.java file. Like most other languages, English includes two types of numbers: cardinal numbers (such as one, two, three, and four) that are used in counting, and ordinal numbers (such as first, second, third, and fourth) that are used to indicate a position in a sequence. In numeric form, ordinals are usually indicated by writing the digits in the number, followed by the last two letters of the English word that names the corresponding ordinal. Thus, the ordinal numbers first, second, third, and fourth often appear in print as 1st, 2nd, 3rd, and 4th. follows: The general rule for determining the SUFFIX of an ordinal can be defined as Numbers ending in the digit 1, 2, and 3, take the suffixes st, nd, and rd, respectively, unless the number ends with the two-digit combination 11, 12, or 13. Those numbers, and any numbers not ending with a 1, 2, or 3, take the suffix th. Your task in this problem is to write a message named createordinalform (n) that takes an integer n and returns a String indicating the corresponding ordinal number. For example, your method should return the following values: createordinalform (1) returns the String 1st createordinalform (2) returns the String 2nd createordinalform (3) returns the String 3rd createordinalform (10) returns the String 10th createordinalform (11) returns the String 11th createordinalform (12) returns the String 12th createordinalform (21) returns the String 21st createordinalform (42) returns the String 42nd createordinalform (101) returns the String 101st createordinalform (111) returns the String 111th You will need to write a main method that tests your createordinalform method by using the above examples.