036valid_sudoku.cpp

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        //set a array to store placehold;
        bool used[9];
        for(int i=0; i<9; ++i){
            fill(used, used+9, false);   //initialize as false;
            /*check one row*/
            for(int j=0; j<9; ++j){
                if(!check(board[i][j], used)){
                    return false;
                }
            }
            /*check one column*/
            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;
        }
        else if(used[ch-'1']){
            return false;
        }
        else{
            used[ch-'1'] = true;
            return true;
        }
    }

};