Sudoku is a logic-based, combinatorial number-placement puzzle which made up of a 9-by-9 grid with nine 3-by-3 sub-grids called boxes. There are 9 rows, 9 columns and 9 boxes in every puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 sub-grids that compose the grid contains all of the digits from 1 to 9. Every puzzle has only one correct solution!
Source from: http://en.wikipedia.org/wiki/Sudoku
