class Solution {
public:
    void solveSudoku(vector<vector<char>>& board) {
        solve(board);
    }
    
    bool solve(vector<vector<char>> &board)
    {
        for(int i=0; i<9; ++i)
        {
            for(int j=0; j<9; ++j)
            {
                if(board[i][j] == ‘.‘)
                {
                    for(int k=0; k<9; ++k)
                    {
                        board[i][j] = k + ‘1‘;
                        if(isValid(board, i, j) && solve(board))
                            return true;
                        board[i][j] = ‘.‘;
                    }
                    
                    return false;
                }
            }
        }
        
        return true;
    }
    
    bool isValid(vector<vector<char>> &board, int i, int j)
    {
        for(int k=0; k<9; ++k)
            if(i != k && board[i][j] == board[k][j])
                return false;
        for(int k=0; k<9; ++k)
            if(j != k && board[i][j] == board[i][k])
                return false;
                
        for(int m=3*(i/3); m<3*(i/3+1); ++m)
            for(int n=3*(j/3); n<3*(j/3+1); ++n)
                if(!(i == m && j == n) && board[i][j] == board[m][n])
                    return false;
                    
        return true;
    }
};

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        for(int i=0; i<9; ++i)
            for(int j=0; j<9; ++j)
                if(board[i][j] != ‘.‘ && !isValid(board, i, j))
                    return false;
                    
        return true;
    }
    
    bool isValid(vector<vector<char>> &board, int i, int j)
    {
        for(int k=0; k<9; ++k)
            if(i != k && board[i][j] == board[k][j])
                return false;
        
        for(int k=0; k<9; ++k)
            if(j != k && board[i][j] == board[i][k])
                return false;
                
        for(int m = 3*(i/3); m<3*(i/3+1); ++m)
            for(int n = 3*(j/3); n<3*(j/3+1); ++n)
                if(!(m == i && n == j) && board[i][j] == board[m][n])
                    return false;
                    
        return true;
    }
};