CSSE 413: Constraint Satisfaction Programming Assignment

Objectives

The purpose of this assignment is to gain first hand experience of what it means to develop artificially intelligent software. You will write software, with little effort, that solves Sudoku problems. Solving them is considered challenging, yet your software will solve them in a fraction of a second.

Assignment

Implement and test a backtracking algorithm to solve Sudoku problems.
Work on the implementation of this assignment by yourself.
Your software needs to read input as follows. The first number, which appears on a row by itself, represents the size of the board. The following numbers represent the given problem. They appear in a grid that corresponds to the boardsize. Each number is separated by whitespace from the others. Below is an example for a 9x9 grid.

9
3 6 0 0 2 0 0 8 9
0 0 0 3 6 1 0 0 0
0 0 0 0 0 0 0 0 0
8 0 3 0 0 0 6 0 2
4 0 0 6 0 3 0 0 7
6 0 7 0 0 0 1 0 8
0 0 0 0 0 0 0 0 0
0 0 0 4 1 8 0 0 0
9 7 0 0 3 0 0 1 4

Your software should output a solution if it exists, or a comment stating that no solution exists. For grading purposes your software also needs to output the solution to a file. The filename should be the same as the input file with the string "Solution" appended after it. For example, if the input file is named "sudoku9Easy.txt" then the output should appear in the file "sudoku9EasySolution.txt". The solution file needs to have the same format as the input file, except, it does NOT contain the first line about the size of the grid. If no solution exists, then you should write -1 to the file.
[40 points] Implement a basic backtracking solver. While it will be able to solve 9x9 problems in a fraction of a second, computational complexity is such that it will not be able to solve 16x16 problems any time today.
Here is some starter code. Feel free to modify, ignore and expand it however you see fit.
Here is some test data.
Please submit a zip archive with the following contents to the appropriate drop-box on Moodle:
- A file called "name.txt" which contains your name.
- Your code
- The solution files for our test data.
- A 400-500 word essay in which you address the following question: "Clearly, solving sudoku problems requires a good amount of intelligence. In what sense is your software intelligent?" Save this file as "essay.txt"
If you are interested in pursuing some extra credit, see whether you can solve the 16x16, 25x25 or 36x36 problems. In order to do so, you will need to implement something like the AC-3 algorithm with some serious inference. The 25x25 and 36x36 will likely only be solvable by using a dynamite data structure such as dancing links. Please talk to me if you want to pursue the extra credit options. We can negotiate point values as well as the deadline.