判断一个 9x9 的数独是否有效。只需要根据以下规则，验证已经填入的数字是否有效即可。
- 数字
1-9在每一行只能出现一次。 - 数字
1-9在每一列只能出现一次。 - 数字
1-9在每一个以粗实线分隔的3x3宫内只能出现一次。
上图是一个部分填充的有效的数独。
数独部分空格内已填入了数字，空白格用 '.' 表示。
示例 1:
输入:
[
["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"]
]
输出: true
示例 2:
输入:
[
["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"]
]
输出: false
解释: 除了第一行的第一个数字从 5 改为 8 以外，空格内其他数字均与 示例1 相同。
但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无效的。
说明:
- 一个有效的数独（部分已被填充）不一定是可解的。
- 只需要根据以上规则，验证已经填入的数字是否有效即可。
- 给定数独序列只包含数字
1-9和字符'.'。 - 给定数独永远是
9x9形式的。
rows:看行是否有重复元素 cols:看列是否有重复元素 cube:看各个9*9是否满足题意。
int rowIndex = 3 * (i / 3);
int colIndex = 3 * (i % 3);
0 1 2 3 4 5 6 7 8
0 0 0 3 3 3 6 6 6 rowIndex
0 3 6 0 3 6 0 3 6 colIndex
0 0 0 1 1 1 2 2 2 j / 3
0 1 2 0 1 2 0 1 2 j % 3
class Solution {
public boolean isValidSudoku(char[][] board) {
for(int i = 0;i < board.length;i++){
HashSet<Character> rows = new HashSet<>();
HashSet<Character> cols = new HashSet<>();
HashSet<Character> cube = new HashSet<>();
for(int j = 0;j < board[0].length;j++){
if(board[i][j] != '.' && !rows.add(board[i][j])) return false; //添加成功返回1
if(board[j][i] != '.' && !cols.add(board[j][i])) return false;
int rowIndex = 3 * (i / 3);
int colIndex = 3 * (i % 3);
if(board[rowIndex + j / 3][colIndex + j % 3] != '.' && !cube.add(board[rowIndex + j / 3][colIndex + j % 3])) return false;
}
}
return true;
}
}
2019-04-29 19:04:12