LeetCode 36. Valid Sudoku (C++)

题目：

Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.

分析：

每一行，每一列没有相同的数字，每一个3*3的小正方形中也没有相同的数字。可以使用数组，map，set等等来判断。

程序：

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        map<char,int> m;
        for (int i = 0; i < 9; i++){
            for (int j = 0; j < 9; j++){
                if (board[i][j] != '.'){
                    if (m[board[i][j]]) return false;
                    m[board[i][j]]++;
                }
            }
            m.clear();
        }
        for (int i = 0; i < 9; i++){
            for (int j = 0; j < 9; j++){
                if (board[j][i] != '.'){
                    if (m[board[j][i]]) return false;
                    m[board[j][i]]++;
                }
            }
             m.clear();
        }
        for (int i = 0; i < 3; i++){
            for (int j = 0; j < 3; j++){
                for (int r = i*3; r < i*3+3; r++){
                    for (int l = j*3; l < j*3+3; l++){
                        if (board[r][l] != '.'){
                            if (m[board[r][l]]) return false;
                            m[board[r][l]]++;
                        }
                    }
                }
                m.clear();
            }
        }
        return true;
    }
};