class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        bool st[9];

        for (int i = 0; i < 9; i ++) {
            memset(st, 0, sizeof(st));
            for (int j = 0; j < 9; j ++) {
                if (board[i][j] != '.') {
                    int t = board[i][j] - '1';
                    if (st[t]) return false;
                    st[t] = true;
                }
            }
        }

        for (int i = 0; i < 9; i ++) {
            memset(st, 0, sizeof(st));
            for (int j = 0; j < 9; j ++) {
                if (board[j][i] != '.') {
                    int t = board[j][i] - '1';
                    if (st[t]) return false;
                    st[t] = true;
                }
            }
        }

        for (int i = 0; i < 9; i += 3) 
            for (int j = 0; j < 9; j += 3) {
                memset(st, 0, sizeof(st));
                for (int x = 0; x < 3; x ++) 
                    for (int y = 0; y < 3; y ++) {
                        if (board[i + x][j + y] != '.') {
                            int t = board[i + x][j + y] - '1';
                            if (st[t]) return false;
                            st[t] = true;
                        }
                    }

            }

        return true;        
    }
};