Sudoku is a logic-based, number placing puzzle game with very simple rules. It originates from Japan, but became popular world wide in the past years. The beauty of sudoku is that the completion rules are simple; yet reaching to the solution requires serious logical reasoning.The goal is to fill the empty cells of the 9x9 board with numbers, so that each column, row and 3x3 subgrid contains the numbers from 1 to 9 exactly once.