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Enough is enough (Posted on 2010-01-29) Difficulty: 3 of 5
In a 9*9 SUDOKU game what is the minimal number of digits guaranteeing a unique solution?

No Solution Yet Submitted by Ady TZIDON    
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Solution If its the second option (spoiler) | Comment 2 of 4 |
--* *** ***
*** 1** 2**
*** 2** 1**

--* *** ***
*** *** *21
*** *12 ***

**1 *2* ***
**2 **1 ***
*** *** *12
In this grid there are only 4 blank cells, marked with dashes.  Each of them must be either a 1 or a 2 but there are two possibilities for which goes where.  Thus the puzzle is not unique even though 77 digits are filled.  (3 through 9 are marked with *s)

As a result 78 digits is the minimum that always guarantees a unique solution.

  Posted by Jer on 2010-01-29 15:45:34
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