36. 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.

本题是比较有趣的一道题，查看数独是否为有效的valid，难点在于正方形的判断的坐标上，代码如下：

public class Solution {
    public boolean isValidSudoku(char[][] board) {
        for(int i=0;i<9;i++){
            Set<Character> row = new HashSet<Character>();
            Set<Character> col = new HashSet<Character>();
            Set<Character> dia = new HashSet<Character>();
            for(int j=0;j<9;j++){
                if(board[i][j]!='.'&&row.contains(board[i][j])){
                    return false;
                }else{
                    row.add(board[i][j]);
                }
                if(board[j][i]!='.'&&col.contains(board[j][i])){
                    return false;
                }else{
                    col.add(board[j][i]);
                }
                if(board[i/3*3+j/3][i%3*3+j%3]!='.'&&dia.contains(board[i/3*3+j/3][i%3*3+j%3])){
                    return false;
                }else{
                    dia.add(board[i/3*3+j/3][i%3*3+j%3]);
                }
            }
        }
        return true;
    }
}