| Ruud Site Admin
| Joined: 17 Sep 2005 | Posts: 708 | : | Location: Netherlands | Items |
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Posted: Wed Dec 21, 2005 3:26 pm Post subject: |
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Hi Anthony,
Uniqueness is usually checked by a backtracking technique, like Dancing Links. This is because a non-unique Sudoku may have 77 solved cells, and only 4 unsolved with 2 possibilities to complete it.
Checking only a random single cell will only tell you that cell has only one option, but it does not tell you anything about the other 80 cells.
However, if you only want to prove non-uniqueness, testing a single cell can tell you that, because if it allows multiple digits, you know the puzzle has multiple solutions.
Ruud. _________________ Meet me at sudocue.net |
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