Leetcode题目036. 有效的数独

class Solution
{
public:
    bool isValidSudoku(vector<vector<char>>& board)
{
        
        for (int i = 0; i < 9; i++) //每一行中不能有重复
        {
            unordered_set<char> used_chars;
            for (int j = 0; j < 9; j++)
            {
                char ch = board[i][j];
                if(ch == '.') continue;
                if (used_chars.find(ch) != used_chars.end()) //能找到！
                    return false;
                else
                    used_chars.insert(ch);
            }
        }

        for (int j = 0; j < 9; j++) //每一列中不能有重复
        {
            unordered_set<char> used_chars;
            for (int i = 0; i < 9; i++)
            {
                char ch = board[i][j];
                if(ch == '.') continue;
                if (used_chars.find(ch) != used_chars.end()) //能找到！
                    return false;
                else
                    used_chars.insert(ch);
            }
        }

        for(int R=0; R<3; R++) //每一个以粗实线分隔的 3x3 宫内不能有重复
        {
            for(int C=0; C<3; C++)
            {
                unordered_set<char> used_chars;
                for(int i = 3 * R; i < 3 * R + 3; i++)
                {
                    for (int j = 3 * C; j < 3 * C + 3; j++)
                    {
                        char ch = board[i][j];
                        if(ch == '.') continue;
                        if (used_chars.find(ch) != used_chars.end()) //能找到！
                            return false;
                        else
                            used_chars.insert(ch);
                    }
                }
            }
        }

        return true;
    }

};