Final Project: Verify a Sudoku Solution Due Fri Apr 29 (2400 hrs)? Wed May 4 (1200 hrs)? 1

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1 Final Project: Verify a Sudoku Solution Due Fri Apr 29 (2400 hrs)? Wed May 4 (1200 hrs)? 1 A. Why? A final project is a good way to have students combine topics from the entire semester, to see how they interact. B. Objectives At the end of this project, you should: Be able to write parts of a C++ program of moderate size (a few hundred lines of code). Be able to open files; read and traverse two-dimensional arrays; and use nested loops. Be able to break up pieces of large code into collections of smaller functions. C. Verify a Sudoku Puzzle Solution For your final project, you are to write a C++ program that reads a representation of a Sudoku board and determine whether or not it's a correct solution. Note: You're not going to play a game, just check a possible solution for correctness. The credit for the project covers not just functionality ("Does it work?") but also readability ("Are there comments to explain what it does?" and "Is it well-organized?") D. So What's Sudoku? A Sudoku puzzle is an extended Latin Square problem. In a Latin square, you fill an n n square with the digits 1 n so that no row or column contains the same value twice. Here's a 3 3 example: A Sudoku puzzle has a 3 3 grid of 3 3 boxes (so, 9 9 cells altogether). The object is to get each row, column, and 3 3 box to have exactly the digits 1 9 (without omitting or repeating digits). Here s an example, with the rows and columns labeled 1 9. (Stolen from puzzle 1730.) 1 Apr 29 is the last Friday before final exams; May 4 is the day of the final exam; let's discuss in class which date to make the project due. CS 105: Intro Computer Pgmg I - 1 of 5 - James Sasaki, 2011

2 In an actual Sudoku puzzle, most of the cells are empty and one's task is to fill in the missing values. There are a number of programs available that solve Sudoku puzzles, but that's not our project we're going to read a 9 9 grid of numbers and determine whether or not it's a correct solution. If it isn't, we'll print error messages pointing out where cells match when they shouldn't; at the end, we'll also print the total number of errors. E. Possible Sample Runs To illustrate how your program should work, here's a sample run of a possible solution. It asks for a file containing a puzzle, reads in and echos out the puzzle, and then checks it for correctness: Each row has to have 9 different values; each column has to have 9 different values, and each box has to have 9 different values. What follows are possible sample outputs. Your output should have the same content, though your wording doesn't have to be identical. In the sample below, the input file contains a correct puzzle solution. User input is underlined italic. CS 105: Intro Computer Pgmg I - 2 of 5 - James Sasaki, 2011

3 Enter name of file with solution to test: sdok.dat Reading file sdok.dat... The Sudoku puzzle: Checking rows... no errors Checking cols... no errors Checking boxes... no errors The puzzle solution is correct. Now here's a run with an incorrect solution. Enter name of file with solution to test: sdbad.dat Reading file sdbad.dat... The Sudoku puzzle: Checking rows... In row 1, cols 1 and 2 are both 1 In row 2, cols 2 and 4 are both 5 In row 3, cols 5 and 9 are both 6 In row 4, cols 6 and 9 are both 7 In row 9, cols 1 and 9 are both 9 Checking cols... In column 2, rows 1 and 9 are both 1 CS 105: Intro Computer Pgmg I - 3 of 5 - James Sasaki, 2011

4 In column 4, rows 2 and 4 are both 5 In column 5, rows 3 and 4 are both 6 In column 9, rows 1 and 9 are both 9 In column 9, rows 4 and 6 are both 7 Checking boxes... In box 1, row 1 col 1 and row 1 col 2 are both 1 In box 2, row 1 col 5 and row 2 col 4 are both 5 In box 2, row 1 col 6 and row 3 col 5 are both 6 In box 6, row 4 col 9 and row 6 col 9 are both 7 In box 9, row 7 col 7 and row 9 col 9 are both 9 Note: Boxes are numbered 1 9 from left to right, top to bottom. The puzzle solution is incorrect: It has 1. Here's a run with a nonexistent input file. Enter name of file with solution to test: nosuchfile.txt Couldn't open input file nosuchfile.txt. Halting execution. And here's a run where the file doesn't have enough data (it only had 3 values): Enter name of file with solution to test: shortfile.dat Reading file shortfile.dat... Couldn't read a value for row 1, col 4. Halting execution. F. Completing a Skeleton A full solution for this problem is fairly long, especially once you include enough comments to make the program more understandable. Since we don't have a lot of time for the project, instead of writing a full program, you're going to complete a skeleton program, sudoku_skeleton.cpp. A skeleton is the framework of a solution but has missing pieces. The missing pieces are usually "stubs." A stub is a subroutine that isn't completely written it's an approximation of what really needs to be done. For example, a stub that calculates a number might just return zero. Having a stub lets you write the routine that calls the stub separately from the stub. For example, the skeleton program uses a checkrows(grid) subroutine that checks each cell to make sure that there's no cell to its right that has the same value. It does this by calling checkrowcell(grid, row, col, value) for each row and column (with value being the number at the given row and column. But the checkrowcell routine, a stub, just prints out a message saying it was called. This lets us make sure that that the checkrows routine is making the correct calls to checkrowcell (i.e., exactly one call for each cell in the puzzle grid). G. Point Breakdown [100 pts total] [5 pts] Read the board (normal case) [5 pts] Check for non-existent input file CS 105: Intro Computer Pgmg I - 4 of 5 - James Sasaki, 2011

5 [5 pts] Check for input file that contains an error [5 pts] Print out the board (2 pts extra credit if you add an extra space between columns 3 and 4; columns 7 and 8; rows 3 and 4; rows 7 and 8). [6 pts] Check the rows (-2 points if you don't avoid duplicate error messages2). [12 pts] Check the columns (-2 points if you don't avoid duplicate error messages). [22 pts] Check the boxes (-5 points if you don't avoid duplicate error messages). [10 pts] Output (including error messages) is complete and readable. [10 pts] Each function you add has a block comment saying what it does. [10 pts] The comments are accurate (if it says a function or piece of code does something, then your code actually does it). [5 pts] The comments should mention everything important that a routine does [5 pts] The code you add/modify is well-organized. (You don't have huge routines with 17 levels of nesting, but you also don't have a zillion subroutines that are each only one line long. H. Submitting Your Program Submit your program using the Assignments folder under Blackboard for the course. (To get to blackboard, log into the myiit portal site.) Document History 4/19/11: Ver. 1.1: Changed to Times font because of printing bug. In red: Added info on box numbering; fixed two typos. CS 105: Intro Computer Pgmg I - 5 of 5 - James Sasaki, 2011