给一个只包含 0， 1， ＊ 的 String，将所有的＊ 替换成 0 或者 1， 返回所有的可能行

void GetAllString(int start, string & str, vector<string> & res)
 {
     if (start == str.size())
     {
         res.push_back(str);
     }
     else
     {
         bool has = false;
         for (int i = start; i < str.size(); i++)
         {
             if (str[i] == ‘*‘)
             {
                 str[i] = ‘1‘;
                 GetAllString(i + 1, str, res);
                 str[i] = ‘2‘;
                 GetAllString(i + 1, str, res);
                 str[i] = ‘*‘;
                 has = true;
                 break;
             }
         }
         if (!has)
             res.push_back(str);
     }
 }

 vector<string> GetAllString(string str)
 {
     vector<string> res;
     GetAllString(0, str, res);
     return res;
 }