Valid Sudoku

Determine whether a Sudoku is valid.

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

Have you met this question in a real interview? 

Yes

Example

The following partially filed sudoku is valid.

Note

A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

Clarification

What is Sudoku?

• http://sudoku.com.au/TheRules.aspx
• https://zh.wikipedia.org/wiki/%E6%95%B8%E7%8D%A8
• https://en.wikipedia.org/wiki/Sudoku
• http://baike.baidu.com/subview/961/10842669.htm

class Solution {
    /**
      * @param board: the board
        @return: wether the Sudoku is valid
      */
    public boolean isValidSudoku(char[][] board) {
        if(board == null || board.length == 0 || board[0].length == 0) return false;
       
        int m = 9, n = 9;
        // check row
        boolean[] visited = new boolean[9];
        for(int i = 0; i < m; i++){
            Arrays.fill(visited, false);
            for(int j = 0; j < n; j++){
                if(!precess(visited, board[i][j])) return false;
            }
        }
       
        for(int i = 0; i < n; i++){
            Arrays.fill(visited, false);
            for(int j = 0; j < m; j++){
                if(!precess(visited, board[j][i])) return false;
            }
        }
       
        for(int i = 0; i < m; i+=3){
       
          for(int j = 0; j < n; j+=3){
              Arrays.fill(visited, false);
              for(int k = 0; k < 9; k++){
                  if(!precess(visited, board[i+k/3][j+k%3])) return false;
              }
               
            }
        }
        return true;
       
    }
   
    private boolean precess(boolean[] visited, char c){
        if(c == '.') return true;
        int num = c - '0';
        if(num > 9 || num < 1 || visited[num-1]) return false;
        visited[num-1] = true;
        return true;
    }
};