Package g0001_0100.s0036_valid_sudoku

Class Solution

  • public class Solution
extends Object
    36 - Valid Sudoku.

    Medium

    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:

    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: true

    Example 2:

    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: false

    Explanation: Same as Example 1, except with the 5 in the top left corner being modified to 8. Since there are two 8’s in the top left 3x3 sub-box, it is invalid.

    Constraints:

    • board.length == 9
    • board[i].length == 9
    • board[i][j] is a digit 1-9 or '.'.

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • isValidSudoku

        public boolean isValidSudoku​(char[][] board)