# 3: Squares and the Board CSCI 4526 / 6626 Solution

1 Goals
• To use default constructors and constructors with parameters.
• To use an input file to construct an array of objects.
• To model the Sudoku board.
2 The Board Class
A traditional sudoku board is a 9 by 9 array of squares. Sometimes we want to view this array as two-dimensional but at other times, we want to view it as a flat array. Various data structures could be used to represent this array, but we will use a simple flat array of 81 Squares and provide the 2-D subscripting through a subscript function.
Normally, an array of 9 things would be accessed using subscripts 0. . . 8. For Sudoku, this turns out to be endlessly confusing, so the player will use 1-based subscripting instead. This means that every player input (1–9) must be converted to a 0-based value (0–8) before using it. Further, the player will input both row and column numbers. Our program will take these two 1-based subscripts and combine them into a single 0-based subscript. This is a nuisance, but better than
the alternative (a confused player who thinks the interface is ugly).
To do. Add another pair of files to your project to implement a Board class. Put the following parts into Board. (More parts will be added next week.)
• #include commands for "tools.hpp" and "Square.hpp" must be at the top of Board.hpp.
• #include "Board.hpp" must be at the top of Board.cpp. No other include commands belong in the cpp file.
• A private array of 81 Squares named bd. (NOT pointers to Squares.)
• A private ifstream that will be used to read in the data for a puzzle.
• A destructor that prints a trace comment.
• A constructor: Board(const char* filename); Print a trace comment. Open the named file. (Call fatal() if this step fails.) The input file will have 9 lines, each consisting of 9 data characters and a newline. A data character is a dash or a digit 1..9. Execute a nested loop for j =1..9 and k = 1..9 to:
– Read the next character from the file.
– If it is a data character, construct a Square using that character and the row and column subscripts, j and k. Store that square in the next slot of the array bd. Use j and k and the subscript function, below, to calculate that slot number.
– After storing the square in bd, if k equals 9, read another character and verify that it is a newline.
– After creating 81 squares, verify that you are at the end of the file. Do this by attempting to read one more character and testing for eof.
– If any step finds an error in the input file format, call fatal. (Soon, we will replace the calls on fatal by throwing exceptions.)
3: Squares and the Board CSCI 4526 / 6626 Spring 2014 2
• A subscript function, Square& sub( int j, int k ) that uses the 2D square coordinates to compute and return a reference to Square object in the Board’s array. The formula is: (j − 1) ⇤ 9 + (k − 1)
• A print function that prints all of the squares on the board, one per line, with a blank line after every 9th square. Delegate the task of printing a square to the print function in the Square class.
• Outside the class but inside the .hpp file, declare an inline method for the output operator: inline ostream& operator<< (ostream& out, Board& b);
It must call your print() function with the appropriate stream parameter and return the ostream&.
Hints:
• You do NOT need dynamic allocation for anything.
• Use this syntax inside the loop to create a Square object and copy it into the proper position in Board’s array: bd.sub(j, k) = Square(input, j, k);
• After debugging on-screen, send your output to a file so you can turn it in. At this time, there is too much output to use cut-and-paste techniques.

Construct a test plan for Board. (Assuming that the Square class works properly.) Incorporate this test plan into a function called testBoard(). Change main() to call both testSquare() and testBoard().
Make a folder for turning in your work. The name of the folder should include both your name and the problem number. This problem is Sudoku-3. (Example: S3-Fischer). Put copies of your test plans, your source code (.cpp and.hpp files) and your output into this directory, then zip it up.