So. You think you're smart. Well, Finnish mathematician Arto Inkala challenges
you to a game of sudoku, the hardest one ever constructed (on the scale
of 1 to 5 as rated by difficulty, this sudoku goes all the way to eleven):
Link
(Give up? Here's the answer)
943682175
675491283
154237896
369845721
287169534
521974368
438526917
796318452
869472153
213658947
475391286
154937628
386245791
927186534
531724869
748569312
692813475
On the other alleged world's hardest Sudoku AI Escargot, my solution is
162857493
534129678
789643521
475312986
913586742
628794135
356478219
241935867
897261354
These were challenging but did not even take a day much less 3 months, unless that was the time Arto Inkala spent to develop them