Program 1: Generating Summation Puzzles

Transcription

1 Program 1: Generating Summation Puzzles Owen Kaser October 3, 2015 Due: 15 October 2015, end of class. 1 Introduction Textbook section gives pseudocode to solve a given summation puzzle. We want to make summation puzzles to annoy our friends, by finding summation puzzles for their names. For instance, I might discover that kaser + ear = karma (a=0, k=1, s=2, e=3, m=4, r=5), or that kaser + err = alas. In this programming project, you will make a Maven-created Java project to accept a word (we ll assume it is your friend s name) as a command-line argument, and then print a sorted list, without duplicates, of all summation puzzles that start with your friend s (lower-case) name. Traditionally, summation puzzles are not supposed to include solutions where the numbers would have leading zeros, so do not generate summation puzzles whose solutions all require leading zeros. Use a brute-force algorithm, as in Code Fragment 5.11, where you go through all ways of assigning lower-case letters to the digits 0 through 5. (You will probably discover that it would take too long to go through 0 to 9 when you use the approach required for this assignment.) Use the words of length 8 or less in the file corncob lowercase.txt that I have checked into your repository 1. If the 6 assigned letters include all of the letter in your friend s name and in a word from this list, check whether sum (as a decimal number) involves only the digits 0 to 5. If so, check whether the sum (encoded) is a valid word from the list. (Note that if your friend has more than 6 different letters in her name, there will be no solutions. The program is likely to produce uncomfortably many solutions if there are only a few distinct letters in her name. If there are five different letters, the output will probably be reasonable.) 1 It s from 1

2 2 Details A variety of requirements ensure that your program can be properly handled during grading. They must be followed, or the likely outcome is that we will assume that your program does not work. If the grader has to do extra work to test your program, because you did not follow these requirements, you can expect lose many points. 1. You must use Maven, in the project that was set up in the lab/tutorial. 2. The main class must be called WP and implement the interface WPInterface, which has already been checked into the repository (the same place as App.java, and the same place where you will write WP.java. Class WP contains the methods psolve, searchsolution, converttonumber, and converttostring as described below. 3. As soon as you create WP.java, add it to version control (svn add). Thereafter, every minutes when you are actively working on coding or debugging it, do a commit operation (svn ci). This serves several purposes. First, it is making a backup for you. Second, it lets me see who is working, and when. Third, it provides some assurance you didn t use a we do your homework for a modest fee service. Finally, if you want to ask me for any help, I can have your problem code right in front of me. You can lose marks on the program if you don t do commits frequently enough. 4. Your friend s name is specified as a command-line argument when the program is run. 5. There is a method producing lines with a format similar to kaser + basks = areas using rksbea The summation puzzle consists of the three words (kaser, basks and areas) with the + and = as shown. Follow this format exactly, except that anything after the final word of a summation puzzle is optional and won t be graded. (In the case of the example above, the optional using rksbea indicates that r=0, k=1, s=2, b=3, e=4 and a=5. This is handy during debugging and in case your friend challenges you to show that some embarrassing summation puzzle actually is valid.) The sorted list is to be produced by a method public List<String> psolve(char [] u, String victim) where the value in victim will be the first word in every puzzle. The character array u serves as the set U (see Code Fragment 5.11). In normal use, array u will contain the 26 lower-case letters. However, for grading/testing, we may use a subset of the letters. So do not assume that the array will always have length Do not use fancy data structures, such as Set, that we have not studied yet. Arrays, Lists and ArrayLists may be used. 2

3 7. A summation puzzle will be listed only once, even if it has multiple solutions. 8. All collections (eg, ArrayList, List etc.) are those in java.util, not from the textbook s data structures library (net.datastructures). 9. WP has a constructor WP(java.util.List<String>) that takes the vocabulary of strings that can appear as the second and third words of the puzzles. (Under normal use, you will pass in a big ArrayList that you get by reading from file corncob lowercase.txt, downloaded from the location indicated in the Introduction. Grading tests may end up using shorter vocabulary lists.) 10. There will be a method List<String> searchsolution(string victim, String encoding) that returns all possible summation puzzles, in no particular order, for a particular first word and a particular encoding. (The encoding is expressed as a String: the first character is the encoding for 0, the second character is the encoding of 1, and so forth. rksbea has the meaning given earlier: r=0, k=1,....) The second and third words of the puzzle are, of course, taken from the vocabulary passed into the constructor. I expect that you will actually need to use this method in your solution, but if you end up doing something crazy that doesn t need its use for the overall program, you still need it as part of the assignment. 11. There will be a method int converttonumber(string word, String encoding) that converts a word (eg kaser into the corresponding integer. So if encoding is rksbea, then kaser is converted to the integer If any character of parameter word does not occur in encoding, the method should return -1. So converttonumber( phaser, rksbea ) would return -1. Also, any word that decodes to a number with a leading 0 (which is illegal) makes the method return -1. So converttonumber( reeks, rksbea ) would return -1, rather than There will be a method String converttostring(int x, String encoding) that is the inverse operation to converttonumber. Given a number x (that has no 6, 7, 8 or 9 when written in decimal), it applies the encoding to form a word. The word may (or may not) be a valid vocabulary word that can occur in puzzles. For example, converttostring(123, rksbea ) gives ksb. If x has a forbidden digit when written in decimal, this method should return the empty string. 3

4 Again, you need this method (and converttonumber for the assignment, even if you don t end up using them to create the summation puzzles. (But I suspect that you will find these two methods helpful.) 13. Your solution will be based around an implementation and modification of the Algorithm PuzzleSolve on page 213. It will not be an exact implementation that solves a particular summation problem (and is then called in a loop for every potential summation problem). Instead, when k=1 it will do something like calling searchsolution. 3 Notes and Hints I took some liberties when implementing PuzzleSolve. For instance, rather than modifying and later restoring U and S, I chose to create a new copy of U and a new copy of S. (There are probably some performance disadvantages to what I did.) You also can make these kinds of adjustments. My sample solution is only about 150 lines long, if I don t count the javadoc comments. However, recursion is tricky. I have office hours and a door that is frequently open on Monday, Tuesday, and Thursday. If you need clarifications or hints, I can probably help. Don t wait till the last minute: it s highly unlikely I ll be available to help at 2am the night of the due date Grading We will grade the final checkin done via subversion, using the last submission date to determine whether the program is late. No printout needs to be submitted. It should be possible for the grader to run mvn package from the top directory of your Maven project (the one that has subdirectories src, target etc.) and then run java -classpath target/j2xs5-1.0-snapshot.jar ca.unbsj.cs2383.wp susie where appropriate substitutions are done for j2xs5. Item Value psolve 5 constructor 5 puzzlesolve 25 converttonumber 12 converttostring 13 searchsolution 10 overall run (includes everything) Since this is not a software-engineering course, points will not be deducted for somewhat suboptimal style. However, if formatting, naming and struc- 4

5 ture are so bad that the grader has difficulties determining what you ve done, you will lose marks. 2. Significant inefficiencies, particularly from not using appropriate data structures that have been covered in class, will result in loss of points. (This rule will be more important with future programs.) If this program takes more than 15 minutes on a lab machine, it is too slow. You should put a prominent comment (or a print statement) warning the grader about excessive run time, if the program will eventually finish. Otherwise, your program might be incorrectly assumed to have an infinite loop. 3. Code that does not compile is worth very little. If you can comment out non-compiling code and get something interesting that compiles, do so. 4. Suppose you have a program that is supposed to do A, then B, then C. While A and C seem to work properly, B usually crashes and thus C does not run. It would be better for you to comment out B. That way, the grader will see that A and C work and you will get some part value for the commented out B. Otherwise, it will be assumed that both B and C are broken. 5