World’s Toughest Sudoku

According to DailyMail in August 2010, linked here is the world’s toughest sudoku at the time.

It was created by Dr. Arto Inkala, an environmental scientist with a doctorate in applied mathematics. It was generated by a computer program that he devised. The puzzle has only one solution and can take someone 3 days to solve by logic.

The article says

“So its difficulty – and frustration factor – lies in the number of mental leaps needed to complete each square.

Like chess, those trying to solve it will have to think several moves ahead. Many exasperating deadends have also been built in.”

The solution is linked here.

You can play sudoku online here.