In a 9*9 SUDOKU game
what is the minimal number of digits guaranteeing a unique solution?
--* *** ***
*** 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.
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Posted by Jer
on 2010-01-29 15:45:34 |
If its the second option (spoiler)
