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.

遍历整个棋盘，只要每行，每列，每个9方格块都没有重复的1-9数字就是一个有效的棋盘；没啥算法，直接看下边代码好了。

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class Solution {
public:
    bool isValidSudoku(vector<vector<char> > &board) {
        if (board.size() != 9) throw -1;
        if (board[0].size() != 9) throw -1;
        bool rflag[9][9] = {false}, cflag[9][9] = {false}, bflag[9][9] = {false};
        for (int i = 0;i < 9; i++) {
            for (int j = 0; j < 9; j++) {
                if (!isdigit(board[i][j])) continue;
                int cval = board[i][j] - '1';
                if (rflag[i][cval] || cflag[j][cval] || bflag[i - i % 3 + j / 3][cval]) return false;
                rflag[i][cval] = cflag[j][cval] =  bflag[i - i % 3 + j / 3][cval] = true;
            }
        }
        
        return true;
    }
    
    
};