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Minimal Number Of Givens ?

 
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Ema Nymton



Joined: 17 Apr 2009
Posts: 89
PostPosted: Sun Apr 19, 2009 11:27 am    Post subject: Minimal Number Of Givens ? Reply with quote
.

Is there a minimal number of givens at which point it becomes impossible to solve a standard sudoku puzzle?

From my personal experience, I have been able to solve a puzzle with 23 givens.

~@:o?
.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sun Apr 19, 2009 1:11 pm    Post subject: Reply with quote
The minimum number of clues is 17. No one has proved this, but no one has found a valid (unique solution) Sudoku with 16 clues.

Surprisingly, these puzzles tend not to be very difficult. (I read that somewhere.) There is a collection here:

http://people.csse.uwa.edu.au/gordon/sudokumin.php

Here is one of them:

Code:

+-------+-------+-------+
| . . . | . . . | . 1 . |
| 4 . . | . . . | . . . |
| . 2 . | . . . | . . . |
+-------+-------+-------+
| . . . | . 5 . | 4 . 7 |
| . . 8 | . . . | 3 . . |
| . . 1 | . 9 . | . . . |
+-------+-------+-------+
| 3 . . | 4 . . | 2 . . |
| . 5 . | 1 . . | . . . |
| . . . | 8 . 6 | . . . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

Here is another:
Code:

+-------+-------+-------+
| . . . | . . . | . 1 . |
| 4 . . | . . . | . . . |
| . 2 . | . . . | . . . |
+-------+-------+-------+
| . . . | . 5 . | 6 . 4 |
| . . 8 | . . . | 3 . . |
| . . 1 | . 9 . | . . . |
+-------+-------+-------+
| 3 . . | 4 . . | 2 . . |
| . 5 . | 1 . . | . . . |
| . . . | 8 . 7 | . . . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

Keith
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