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请你判断一个 9 x 9 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。（请参考示例图）
 

注意：

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。
空白格用 '.' 表示。
 

示例 1：

输入：board = 
[["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：board = 
[["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。
 

提示：

board.length == 9
board[i].length == 9
board[i][j] 是一位数字（1-9）或者 '.'

class Solution {
    public boolean isValidSudoku(char[][] board) {
        
        for(int i=0;i<9;i++){
            boolean[] isExit1 = new boolean[9];
            for(int j=0;j<9;j++){
                if(board[i][j] == '.'){
                    continue;
                }
                int num = board[i][j] - '1';
                if(isExit1[num]){
                    return false;
                }else{
                    isExit1[num] = true;
                }
           }
        }

        
        for(int i=0;i<9;i++){
            boolean[] isExit2 = new boolean[9];
            for(int j=0;j<9;j++){
                if(board[j][i] == '.'){
                    continue;
                }
                int num = board[j][i] - '1';
                if(isExit2[num]){
                    return false;
                }else{
                    isExit2[num] = true;
                }
           }
        }

        
        for(int i=0;i<9;i+=3){
            for(int j=0;j<9;j+=3){
                boolean[] isExit3 = new boolean[9];
                for(int x=0;x<3;x++){
                    for(int y=0;y<3;y++){
                        if(board[i+x][j+y] == '.'){
                            continue;
                        }
                        int num = board[i+x][j+y] - '1';
                        if(isExit3[num]){
                            return false;
                        }else{
                            isExit3[num] = true;
                        }
                    }
                }

            }
        }
    return true;
    }
}