36. Valid Sudoku
1. Question
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.
2. 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.
3. Examples
Example 1:
![img](https://cdn.jsdelivr.net/gh/rootwhois/oss@main/uPic/250px-Sudoku-by-L2G-20050714.svg-20210917142238575.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.
4. Constraints
board.length == 9
board[i].length == 9
board[i][j]
is a digit1-9
or'.'
.
5. References
来源:力扣(LeetCode) 链接:https://leetcode-cn.com/problems/valid-sudoku 著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
6. Solutions
行、列、方块中1-9计数
class Solution {
public boolean isValidSudoku(char[][] board) {
int[][] row = new int[9][9];
int[][] col = new int[9][9];
int[][][] arr = new int[3][3][9];
for (int i = 0; i < board.length; i++) {
for (int j = 0; j < board[0].length; j++) {
if (board[i][j] == '.') {
continue;
}
// 下标从0开始
int val = board[i][j] - '0' - 1;
row[i][val] += 1;
col[j][val] += 1;
arr[i / 3][j / 3][val] += 1;
if (row[i][val] > 1 || col[j][val] > 1 || arr[i / 3][j / 3][val] > 1) {
return false;
}
}
}
return true;
}
}