Q: How do we use constraint propagation to solve the naked twins problem?
A: I'm going through each unit, checking for matches where the length of the current value for a box is equal to the number of occurences of that value within the unit, and that length is greater than one. For the matches, I remove those digits from all the other boxes in the same unit. This propagates the constrained to the rest of the boxes in the unit.
Note, this implementation is not limited to two squares in a unit with identical values of length two; it can deal with three boxes with equal values of length three, four boxes of length four, etc.
Q: How do we use constraint propagation to solve the diagonal sudoku problem?
A: I add the two diagonals to the list of units. This ensures that the constraint of having each diagonal having each digit exactly once is maintained, as our existing rules ensure that each unit has each digit exactly once.
This project requires Python 3.
We recommend students install Anaconda, a pre-packaged Python distribution that contains all of the necessary libraries and software for this project. Please try using the environment we provided in the Anaconda lesson of the Nanodegree.
Optionally, you can also install pygame if you want to see your visualization. If you've followed our instructions for setting up our conda environment, you should be all set.
If not, please see how to download pygame here.
solution.py- You'll fill this in as part of your solution.solution_test.py- Do not modify this. You can test your solution by runningpython solution_test.py.PySudoku.py- Do not modify this. This is code for visualizing your solution.visualize.py- Do not modify this. This is code for visualizing your solution.
To visualize your solution, please only assign values to the values_dict using the assign_value function provided in solution.py
Before submitting your solution to a reviewer, you are required to submit your project to Udacity's Project Assistant, which will provide some initial feedback.
The setup is simple. If you have not installed the client tool already, then you may do so with the command pip install udacity-pa.
To submit your code to the project assistant, run udacity submit from within the top-level directory of this project. You will be prompted for a username and password. If you login using google or facebook, visit this link for alternate login instructions.
This process will create a zipfile in your top-level directory named sudoku-.zip. This is the file that you should submit to the Udacity reviews system.