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.

玩过九宫格的都应该知道规则（没玩过的可以试玩一下九宫格）

（1）每行1~9各出现一次

（2）每列1~9各出现一次

（3）每个小的3宫格，1~9各出现一次

class Solution {
public:

    bool isValidRow(vector<vector<char> >& board){
        for(int row = ; row < ; ++ row){
            vector<int> cnt(,);
            for(int col = ; col < ; ++ col){
                char item = board[row][col];
                if(item != '.'){
                    if(cnt[item-'']!=) return false;
                    else cnt[item-'']++;
                }
            }
        }
        return true;
    }

    bool isValidCol(vector<vector<char> >& board ){
        for(int col = ; col < ; ++ col){
            vector<int> cnt(,);
            for(int row = ; row < ; ++ row){
                char item = board[row][col];
                if(item != '.'){
                    if(cnt[item-'']!=) return false;
                    else cnt[item-'']++;
                }
            }
        }
        return true;
    }

    bool isValidBox(vector<vector<char> >& board){
        for(int i =  ; i < ; ++ i){
            for(int j =  ; j < ; ++ j){
                vector<int> cnt(,);
                for(int row = *i;row < *i+; ++row){
                    for(int col = *j; col < *j+; ++col){
                        char item = board[row][col];
                        if(item != '.'){
                            if(cnt[item-'']!=) return false;
                            else cnt[item-'']++;
                        }
                    }
                }
            }
        }
        return true;
    }

    bool isValidSudoku(vector<vector<char> > &board) {
        return isValidRow(board)&&isValidCol(board)&&isValidBox(board);
    }
};