LeetCode--036--有效的数独(java)
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
1 class Solution { 2 public boolean isValidSudoku(char[][] board) { 3 for(int i = 0;i < board.length;i++){ 4 HashSet<Character> rows = new HashSet<>(); 5 HashSet<Character> cols = new HashSet<>(); 6 HashSet<Character> cube = new HashSet<>(); 7 for(int j = 0;j < board[0].length;j++){ 8 if(board[i][j] != '.' && !rows.add(board[i][j])) return false; //添加成功返回1 9 if(board[j][i] != '.' && !cols.add(board[j][i])) return false; 10 11 int rowIndex = 3 * (i / 3); 12 int colIndex = 3 * (i % 3); 13 14 if(board[rowIndex + j / 3][colIndex + j % 3] != '.' && !cube.add(board[rowIndex + j / 3][colIndex + j % 3])) return false; 15 } 16 } 17 return true; 18 } 19 }
2019-04-29 19:04:12