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?