How many different sudoku puzzles are there?

combinatorics matrices sudoku

The answer: 6, 670, 903, 752, 021, 072, 936, 960, according to this site:

https://www.technologyreview.com/2012/01/06/188520/mathematicians-solve-minimum-sudoku-problem/

I have tried to get this number using direct methods but basically I have found the question too hard. There are too many possibilities, but I am likely missing some strategic ways to solve the problem. Any help would be greatly appreciated, thanks.


Solution 1:

http://www.afjarvis.staff.shef.ac.uk/sudoku/sudoku.pdf ${}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}$

Solution 2:

Try Wikipedia for an introduction and overview and additional references.

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