数字当索引-力扣-一次遍历

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：

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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：

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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 '.'

cpp 复制代码

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
           int row[9][9];
           int low[9][9];
           int m[3][3][9];
        memset(row,0,sizeof(row));
        memset(low,0,sizeof(low));
        memset(m,0,sizeof(m));
        for(int i=0;i<9;i++)
        for(int j=0;j<9;j++)
        {
            if(board[i][j]=='.')continue;
            int index=board[i][j]-'0'-1;
             row[i][index]++;
             low[j][index]++;
             m[i/3][j/3][index]++;
             if(row[i][index]>1||low[j][index]>1||m[i/3][j/3][index]>1) return false;
        }
        return true;
    }
};