Sudoku solver

- Sudoku consists of a 9×9 square grid containing 81 cells. The grid is subdivided into nine 3×3 blocks. Some of the 81 cells are filled in with numbers from the set {1,2,3,4,5,6,7,8,9}. These filled-in cells are called givens. The goal is to fill in the whole grid using the nine digits so that each row, each column, and each block contains each number exactly once. We call this constraint on the rows, columns, and blocks the One Rule.

- Depending on the difficulty of the Sudoku problem, there may be 1 or more results or no results.