创建一个表示是星期几的枚举类型Weekday，用户从键盘输入星期几的英文字符串，输出这是一周中的第几天（星期天是一周中的的第一天）。

好的，让我来回答你的问题。以下是代码示例：

enum Weekday {
  Sunday = 1,
  Monday,
  Tuesday,
  Wednesday,
  Thursday,
  Friday,
  Saturday
};

int main() {
  std::string input;
  std::cout << "Please input a weekday (e.g. Monday): ";
  std::cin >> input;

  int day = 0;
  if (input == "Sunday") {
    day = Sunday;
  } else if (input == "Monday") {
    day = Monday;
  } else if (input == "Tuesday") {
    day = Tuesday;
  } else if (input == "Wednesday") {
    day = Wednesday;
  } else if (input == "Thursday") {
    day = Thursday;
  } else if (input == "Friday") {
    day = Friday;
  } else if (input == "Saturday") {
    day = Saturday;
  } else {
    std::cout << "Invalid input" << std::endl;
    return 0;
  }

  std::cout << "This is the " << day << " day of the week" << std::endl;

  return 0;
}

以上代码会创建一个枚举类型Weekday，接着会从用户输入的英文字符串中，根据所输入的星期几，输出这是一周中的第几天。如若输入“Monday”，那么输出“this is the 2nd day of the week”。