Valid Sudoku
Description
Determine if a 9 x 9
Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
- Each row must contain the digits
1-9
without repetition. - Each column must contain the digits
1-9
without repetition. - Each of the nine
3 x 3
sub-boxes of the grid must contain the digits1-9
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:
![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Sudoku-by-L2G-20050714.svg/250px-Sudoku-by-L2G-20050714.svg.png)
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 digit1-9
or'.'
.
Solution(javascript)
/**
* @param {character[][]} board
* @return {boolean}
*/
var isValidSudoku = function(board) {
for (let i = 0; i < 9; i++) {
let row = new Set(), col = new Set(), box = new Set();
for (let j = 0; j < 9; j++) {
let _row = board[i][j];
let _col = board[j][i];
let _box = board[Math.floor(i/3) * 3+ Math.floor(j / 3)][(i % 3) * 3 + (j % 3)]
if (row.has(_row) || col.has(_col) || box.has(_box)) return false;
if (_row !== ".") row.add(_row);
if (_col !== ".") col.add(_col);
if (_box !== ".") box.add(_box);
}
}
return true
};