3.7.250. Sudoku
A constraint that can be used for modelling the Sudoku puzzle problem. A Sudoku square is an array in which 9 distinct numbers in are arranged so that the following two conditions hold:
Each number occurs once in each row and column.
The numbers in each major block are distinct.
Figure 3.7.77. (A)Β A partially filled Sudoku square and (B)Β its unique completion
The Sudoku puzzle problem is to complete a partially filled board in order to get a Sudoku square. PartΒ (A) of FigureΒ 3.7.77 gives a partially filled Sudoku board, while partΒ (B) provides its unique possible completion.