Valid Sudoku
Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.
Note:
- A Sudoku board (partially filled) could be valid but is not necessarily solvable.
- Only the filled cells need to be validated according to the mentioned rules.
Example 1
5 3 . . 7 . . . . 6 . . 1 9 5 . . . . 9 8 . . . . 6 . 8 . . . 6 . . . 3 4 . . 8 . 3 . . 1 7 . . . 2 . . . 6 . 6 . . . . 2 8 . . . . 4 1 9 . . 5 . . . . 8 . . 7 9
Input
board = [["5","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]]Output
trueNo digit is repeated in any row, column, or 3 x 3 sub-box.
Example 2
8 3 . . 7 . . . . 6 . . 1 9 5 . . . . 9 8 . . . . 6 . 8 . . . 6 . . . 3 4 . . 8 . 3 . . 1 7 . . . 2 . . . 6 . 6 . . . . 2 8 . . . . 4 1 9 . . 5 . . . . 8 . . 7 9
Input
board = [["8","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]]Output
falseThe digit 8 appears twice in the first column, so the board is invalid.
Constraints
- board.length == 9
- board[i].length == 9
- board[i][j] is a digit '1' to '9' or '.'