[Leetcode]36. 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)                if (!check(board[i][j], used))                    return false;                                fill(used, used + 9, false);                        for (int j = 0; j < 9; ++j)                if (!check(board[j][i], used))                    return false;        }                for (int r = 0; r < 3; ++r)            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;        return used[ch - '1'] = true;    }};