Sudoku
Sudoku is a logic-based puzzle. It’s a type of constraint problem, where the solver is given a finite number of objects ( the number 1-9) and a set of conditions stating how the objects must be placed in relation to one another. The puzzle consists of 9 x 9 grid further divided into nine 3 x 3 sub-girds. The objective is to place the digits with in the grid so that each column, row and sub-grid contains all of the digits from 1-9. Each puzzle is published with some of the boxes already filled, and those constrains help define the problem’s difficulty. brilliant article on sudoku