Backtracking — SUDOKU Solver

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 (also called “boxes”, “blocks”, “regions”, or “sub-squares”) con­tains all of the dig­its from 1 to 9. The puz­zle set­ter pro­vides a par­tially com­pleted grid, which for a well-posed puz­zle has a unique solu­tion. (Source: Wiki — http://en.wikipedia.org/wiki/Sudoku)

http://algorithms.tutorialhorizon.com/backtracking-sudoku-solver/