Heuristic Repair and Sudoku

1. Heuristic Repair and Sudoku Sharon Hastings Artificial Intelligence

2. What is Heuristic Repair? • Generate a possible solution that is close to the goal • This can be done randomly or using a heuristic • Make changes that reduce the distance of the state from the goal

3. Sudoku Puzzle To solve this puzzle using heuristic repair a possible solution must be generated.

4. This solution is generated by filling in the board, avoiding any conflicts within a 3x3 or a column. The only conflicts that exist are within the rows.

5. Now check the conflicts and use heuristic repair to find the solution. Let’s begin looking at the 9 in the top left 3x3. This 9 has no conflicts. So we can move on to the 7.

6. The 7 has two conflicts. Now, check other places in column of that 3x3. Where the 5 is, 7 would have no conflicts. Swap 5 and 7.

7. Now check 5. 5 has no conflicts in it’s new location. Notice the1 in the top middle 3x3 also has no conflicts. Now, the 7 may be examined.

8. This 7 has one conflict. Where 5 is, 7 still has one conflict. Where 4 is 7 has no conflicts. Swap 7 and 4.

9. Now check 4. 4 has no conflicts. Now examine the 6 in the right top 3x3.

10. The 6 has one conflict. Where 2 is, 6 would have no conflicts. Swap 2 and 6.

11. 2 has no conflicts. No more conflicts exist in the top 3x3 boxes.

12. Now look at the middle row of 3x3 boxes.

13. Now look at the bottom row of 3x3 boxes. SOLUTION!!