[leetcode 36] Valid Sudoku

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本文介绍了一个用于验证数独是否有效的算法实现。该算法检查数独的每一行、每一列及每一个九宫格内的数字是否符合数独规则，即1到9的数字不能重复出现。通过对数独板进行遍历并利用辅助数组来跟踪已使用的数字，可以有效地完成这一验证过程。

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) {
        bool used[9];
        for (int i = 0; i < 9; i++) {
            fill_n(&used[0], 9, false);
            for (int j = 0; j < 9; j++) {
                if (!check(board[i][j], used)) {
                    return false;
                }
            }
            fill_n(&used[0], 9, false);
            for (int j = 0; j < 9; j++) {
                if (!check(board[j][i], used)) {
                    return false;
                }
            }
        }
        for (int row = 0; row < 3; row++) {
            for (int col = 0; col < 3; col++) {
                fill_n(&used[0], 9, false);
                for (int i = row*3; i < row*3 + 3; i++) {
                    for (int j = col*3; j < col*3 + 3; j++) {
                        if (!check(board[i][j], used)) {
                            return false;
                        }
                    }
                }
            }
        }
        return true;
        
    }
    bool check(char ch, bool used[9]) {
        if (ch == '.') {
            return true;
        }
        if (used[ch-'1']) {
            return false;
        }
        return used[ch-'1'] = true;
    }
};