Takes ~30sec on my laptop, using the R library for sudoku:
library("sudoku") solveSudoku(readSudoku("worlds-most-difficult-sudoku.txt")) [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [1,] 1 6 2 8 5 7 4 9 3 [2,] 5 3 4 1 2 9 6 7 8 [3,] 7 8 9 6 4 3 5 2 1 [4,] 4 7 5 3 1 2 9 8 6 [5,] 9 1 3 5 8 6 7 4 2 [6,] 6 2 8 7 9 4 1 3 5 [7,] 3 5 6 4 7 8 2 1 9 [8,] 2 4 1 9 3 5 8 6 7 [9,] 8 9 7 2 6 1 3 5 4
Of course, using a computer might properly be regarded as cheating... :-)
Date: Tue, 7 Nov 2006 23:01:34 +0100 From: "wouter meeussen" <wouter.meeussen@pandora.be>
got a solution in 30 min. using my Mma-solver and manual backtrack; any others?
From: "Christian Boyer" <cboyer@club-internet.fr> To: "'math-fun'" <math-fun@mailman.xmission.com>
+-------+-------+-------+ | 1 . . | . . 7 | . 9 . | | . 3 . | . 2 . | . . 8 | | . . 9 | 6 . . | 5 . . | +-------+-------+-------+ | . . 5 | 3 . . | 9 . . | | . 1 . | . 8 . | . . 2 | | 6 . . | . . 4 | . . . | +-------+-------+-------+ | 3 . . | . . . | . 1 . | | . 4 . | . . . | . . 7 | | . . 7 | . . . | 3 . . | +-------+-------+-------+ -- Steve Rowley <sgr@alum.mit.edu> http://alum.mit.edu/www/sgr/ Skype: sgr000