Computer Science I - Programming Assignment 5

Due Wednesday, December 9th

Summary

For this assignment you will create a web page called sudoku.html that will display a Sudoku puzzle for the user to solve. It should look something like this:

A Sudoku puzzle is a nine by nine grid of numbers (from 1 to 9) with some of the squares in the grid left empty. Additionally the grid is divided into nine three by three sub-grids (usually outlined with a thicker black line). To solve a Sudoku puzzle one must fill in the empty squares with numbers (again from 1 to 9) so that each row, each column, and each sub-grid contains all nine numbers (which means no row, column or sub-grid can contain two or more of the same number.)

For example, the solution to the puzzle above would look like this:

Note that in the examples, in addition to the puzzle itself, there are three buttons and a text box. The three buttons should test to see if the user's answers violate any of the rules described above. Clicking the "Check Columns" button should verify that every number between 1 and 9 appears in each column, and print a message in the text box indicating the result (e.g. "columns are ok" or "columns are not ok". The other two buttons should to the same with respect to the rows and subgrids of the puzzle.

If you want an extra challenge you can indicate which row, column or subgrid violates the rules. Again, make sure to get the required functionality working (and saved) before adding extra features.

Files

I have already implemented the part of the code that constructs the puzzle here: sudoku.html. Your job is to implement the functions CheckRows, CheckColumns, and CheckSubgrids.

Helpful Hints

• You might find it easier to implement functions that check a single row, a single column, and a single subgrid first and then call these functions repeatedly (perhaps in a loop) in your main functions.
• One technique that may simplify checking the rows, columns, and subgrids is to use an array to count the number of times each number is encountered, much like we did with dice in the Yahtzee lab.
• Checking the subgrids is a little trickier than checking rows and columns. It may help to number each subgrid from 1 to 9, in a similar fashion to the way a phone keypad is layed out (i.e. the top three subgrids are 1, 2, and 3, the middle three are 4, 5, and 6, and the bottom three are 7, 8, and 9). Assuming this layout you can calculate the location of the top left square in each subgrid using the following formulas (where sg is the subgrid number):
  • The row of the upper left square is Math.floor((sg - 1)/3) * 3
  • The column of the upper left square is (sg - 1) % 3 * 3
  The % operator in the second formula is known as the modulus operator. In general x % y evaluates to the remainder after dividing x by y. So 0 % 3 is 0, 1 % 3 is 1, and 5 % 3 is 2.

Instructions for Handing In the Program

Please hand in the following:

• a printed copy of your completed sudoku.html in class on the due date
• an electronic copy of this file via FileZilla in the handin folder in your home directory on the CS server.

Do not put your assignment in your html directory as that is publicly viewable.