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.

思路：暴力法。
开辟3个二维数组空间，分别记录行、列、九宫格中是否有1到9的数字，初始化为0，表示没有。两层循环遍历，当有数字时判断，如果没有则有效写1，反之有则无效。

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        int used1[9][9]={0},used2[9][9]={0},used3[9][9]={0};
        for(int i=0;ifor(int j=0;jif(board[i][j]!='.'){
                    int num=board[i][j]-'0'-1,k=i/3*3+j/3;
                    if(used1[i][num]||used2[j][num]||used3[k][num])
                    return false;
                    used1[i][num]=used2[j][num]=used3[k][num]=1;    
                }
            }
        }
        return true;
    }
};