Sudoku is one of the most famous number puzzle in the world. It was originally came from Japan and immediately a hit in 90s. It simply a 9×9 grid consist of number from one to nine. The game has so much simple task to, you have to filled the grid exactly with number one to nine horizontally and vertically at the same way which you may not have the same number in any line. Plus, it has 9 of 3×3 grid that also going to have filled with number one to nine. Is it hard enough?
I played this puzzle since I was in junior high. I bought a book of sudoku collection and become addicted since then. I love it because it doesn’t required anything but your logic and fast thinking about numbers. Beside that, I also played various sudoku games across flatform till today. This journey of endless joy with numbers come into a bit of excitement when I found a news about the world’s hardest sudoku.
Spend your time to solve the puzzle later, cause I don’t want you preoccupied already before finishing this article. Anyway, are you thinking this is may the actual world’s hardest sudoku? How can it be harder?
To answer that, we will move into different question that what is actually the minimum clues that a sudoku need to be solved? Recently, in the beginning of 2012, Gary McGuire and his crew at University College Dublin officially announce that any 16-clue or less sudokus can not be solved. He and his team we’re trying every possible ways, all 6,670,903,752,021,072,936,960 of them, and found nothing but unsolved sudoku. Which now imply that the minimum clues is still 17.
Now, take a look at Mr. Inkala’s puzzle, how many is the clue available? Yes, 21 it is. So, no matter how hard this puzzle be, it always have a way to become more difficult by reducing the number of clue into 17. By doing that, the puzzle still crackable though.
Away from that, if you still curious how Mr. McGuire and his team do brute force method in searching 16-clues sudoku solution, I put a video from marvelous Numberphile, explaining about lucky number 17.