[LeetCode]Valid Sudoku

题目描述:(链接)

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.

解题思路：

先验证行，再验证列，最后验证小方格！

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        bool used[9];
        
        for (int i = 0; i < 9; ++i) {
            memset(used, false, sizeof(used));
            for (int j = 0; j < 9; ++j) {
                if (!isVaild(board[i][j], used)) {
                    return false;
                }
            }
            
            memset(used, false, sizeof(used));
            for (int j = 0; j < 9; ++j) {
                if (!isVaild(board[j][i], used)) {
                    return false;
                }
            }
        }
        
        for (int r = 0; r < 3; ++r) {
            for (int c = 0; c < 3; ++c) {
                memset(used, false, sizeof(used));
                
                for (int i = r * 3; i < 3 * r + 3; ++i) {
                    for (int j = c * 3; j < 3 * c + 3; ++j) {
                        if (!isVaild(board[i][j], used)) {
                            return false;
                        }
                    }
                }
            }
        }
        
        return true;
    }
private:
    bool isVaild(char c, bool *used) {
        if (c == '.') {
            return true;
        }
        
        if (used[c - '1']) {
            return false;
        }
        
        used[c - '1'] = true;
        return true;
    }
};