Difficulty: Medium
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
1-9without repetition. - Each column must contain the digits
1-9without repetition. - Each of the 9
3x3sub-boxes of the grid must contain the digits1-9without 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
1-9and the character'.'. - The given board size is always
9x9.
Language: Java
}
for (int i = 0; i < 9; i++) {
// every row
Set<Character> set = new HashSet<>();
set.addAll(vList.get(i));
set.addAll(vList.get(i + 9));
set.addAll(vList.get(i + 9 * 2));
if (set.size() != (vList.get(i).size() + vList.get(i + 9).size() + vList.get(i + 9 * 2).size())) {
return false;
}
// every columns
Set<Character> set2 = new HashSet<>();
set2.addAll(hList.get(i));
set2.addAll(hList.get(i + 9));
set2.addAll(hList.get(i + 9 * 2));
if (set2.size() != (hList.get(i).size() + hList.get(i + 9).size() + hList.get(i + 9 * 2).size())) {
return false;
}
// every little 9 grips
Set<Character> set3 = new HashSet<>();
set3.addAll(vList.get(i * 3));
set3.addAll(vList.get(i * 3 + 1));
set3.addAll(vList.get(i * 3 + 2));
if (set3.size() != (vList.get(i * 3).size() + vList.get(i * 3 + 1).size() + vList.get(i * 3 + 2).size())) {
return false;
}
}
return true;
}
}