A partially filled sudoku which is valid.
Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.
检测一个数独是否有效,数独的规则大家不明白的可以去百度一下。这里我们只需要检查当前的状态是否有效,而不用找到一个解。所以我们只要检查每行,每列以及没九个小方格内是否都没有重复数字出现就可以了。代码如下:
public class Solution { public boolean isValidSudoku(char[][] board) { HashSet<Character> set = new HashSet<Character>(); for(int i = 0; i < board.length; i++) { for(int j = 0; j < board[0].length; j++) { if(set.contains(board[i][j])) return false; else if(board[i][j] != '.') set.add(board[i][j]); } set.clear(); } for(int i = 0; i < board[0].length; i++) { for(int j = 0; j < board.length; j++) { if(set.contains(board[j][i])) return false; else if(board[j][i] != '.') set.add(board[j][i]); } set.clear(); } for(int m = 0; m < 3; m++) { for(int n = 0; n < 3; n++) { for(int i = 3 * m; i < 3 * m + 3; i++) { for(int j = 3 * n; j < 3 * n + 3; j++) { if(set.contains(board[i][j])) return false; else if(board[i][j] != '.') set.add(board[i][j]); } } set.clear(); } } return true; } }