36. Valid Sudoku

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本文介绍了一种验证数独是否有效的算法实现。该算法检查数独盘面的每一行、每一列以及每一个小九宫格内数字是否重复，确保所有已填数字符合数独规则。

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.

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        int row[9][9] = {0}, col[9][9] = {0}, box[9][9] = {0};
        for(int i = 0; i < 9; ++i)
            for(int j = 0; j < 9; ++j){
                if(board[i][j] != '.'){
                    int num = board[i][j] - '1', k = i/3*3 +j/3;
                    if(row[i][num] || col[j][num]||box[k][num])
                    return false;
                    else
                    row[i][num] = col[j][num] = box[k][num] = 1;
                    
                }
            }
        return true;
    }
};