[LeetCode] 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.

class Solution {public:bool isValidSudoku(vector<vector<char>>& board) {    bool used[9];    for (int i = 0; i < 9; ++i) {        fill(used, used + 9, false);        for (int j = 0; j < 9; ++j) // check for row            if (!check(board[i][j], used))                return false;        fill(used, used + 9, false);                for (int j = 0; j < 9; ++j) // check for column�            if (!check(board[j][i], used))                return false;    }            for (int r = 0; r < 3; ++r) // check for 3x3 grid�        for (int c = 0; c < 3; ++c) {                        fill(used, used + 9, false);                        for (int i = r * 3; i < r * 3 + 3; ++i)                for (int j = c * 3; j < c * 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;        used[ch - '1'] = true;        return true;    }};