36. Valid Sudoku
Determine if a 9x9 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 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.
A partially filled sudoku which is valid.
The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
Example 1:
Input:
[
["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:
[
["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.
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.
- The given board contain only digits 1-9 and the character '.'.
The given board size is always 9x9.
解析
给定一个一个二维数组代表数独的数据,判断是否满足数独的条件。有三个条件一个是:每列不能有重复的字符,每行不能有重复的数字,每个3*3的小块不能有重复的数字。
参考答案(自己写的)
class Solution {
public boolean isValidSudoku(char[][] board) {
List<Set<Character>> colList = new ArrayList<>();
List<Set<Character>> subBoxList = new ArrayList<>();
for (int i = 0; i < 9; i++) {
colList.add(new HashSet<>());
subBoxList.add(new HashSet<>());
}
for (int i = 0; i < board.length; i++) {
Set<Character> row = new HashSet<>();
for (int j = 0; j < board.length; j++) {
if (board[i][j] != '.') {
if (row.contains(board[i][j])) {
return false;
} else {
row.add(board[i][j]);
}
if (colList.get(j).contains(board[i][j])) {
return false;
} else {
colList.get(j).add(board[i][j]);
}
int index = (i / 3) * 3 + j / 3;
if (subBoxList.get(index).contains(board[i][j])) {
return false;
} else {
subBoxList.get(index).add(board[i][j]);
}
}
}
}
return true;
}
}
用2个List<Set