[leetcode]Valid Sudoku

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Valid Sudoku

 Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character ‘.‘.

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.

演算法思路：

逐行逐列判斷行列是否有衝突，然後再逐塊判斷。

從網上看到有位大拿寫的矩陣標記法，第二遍看繼續亮瞎。不敢班門弄斧，然後上人家的演算法吧。

代碼如下：

 1 public class Solution { 2     public boolean isValidSudoku(char[][] board) { 3         if(board == null || board.length != 9 || board[0].length != 9) return false; 4         boolean[][] row = new boolean[9][9]; 5         boolean[][] col = new boolean[9][9]; 6         boolean[][] matrix = new boolean[9][9]; 7         for(int i = 0; i < 9; i++){ 8             for(int j = 0; j < 9; j++){ 9                 if(board[i][j] == ‘.‘) continue;10                 int n = board[i][j] - ‘1‘;11                 if(row[i][n] || col[j][n] || matrix[i - i % 3 + j / 3][n]){12                     return false;13                 }14                 row[i][n] = col[j][n] = matrix[i - i % 3 + j / 3][n] = true;15                 16             }17         }18         return true;19     }20 }