Rules for solving sudoku puzzles.
Sudoku has 5 rules that must be followed in order to complete a board.
- Each square must contain one and only one number.
- Each row must contain no duplicate numbers.
- Each column must contain no duplicate numbers.
- Each section of the board must contain no duplicate numbers.
- Only the number 1 to N can be used, where N is the size of the board.
On a 9x9 board, this essentially comes down to every row, column and board section containing the numbers 1 to 9, with no duplicates in either. An example of a complete board is shown below.
Note that the player has placed a number 6 in the 4th row of the 6th column. This breaks rule 2, 3 and rule 4. Note that the 6th column already has a number 6 in it (highlighted in red), this breaks rule 3. There is also a 6 already in row 4, which is also highlighted in red. This breaks rule 2. The 6 in row 4 is also in the same section as the grey 6, this breaks rule 4.
Correct Sudoku Boards
Below is an example of a correct board.